The first-ever footage of Luigi as a playable character in Super Mario 64 was discovered through an old VHS tape in 2023. The footage was captured by a Japanese broadcaster recording footage of Nintendo's 1995 Space World trade show in Japan for a TV program covering the event. Despite this, the footage of Luigi is not actually the primary focus of the clip and as such can barely be seen at all. The video shows Luigi falling back down after performing a spin-jump in what appears to be a red and white test area.
Originally, going by some of the initial concept art as well as early gameplay footage for Star Fox Adventures, the tip of Krystal's staff was meant to transform whenever Fox performed one of its magic abilities. For example, when Fox performed the Ground Quake ability, it'd transform into a hammer. Curiously, one of the pieces of concept art mentions the staff transforming into a wing tip to give Fox the ability to glide, which goes unused in the final game. The models for these staff transformations were also found within the E3 2002 kiosk version of Star Fox Adventures. Ultimately, this went unused in the final game.
SFA Space World 2001 trailer showing Krystal's staff tip transforming into a hammer when Fox performs the Ground Quake ability: https://youtu.be/OliAnoALccg?t=15
Disney's Animated Storybook: Toy Story and Toy Story Activity Center were developed by a devision of Pixar known as the Interactive Products Group, which exclusively made video game content. The division was closed down when the Toy Story 2 movie entered production, and merged into Pixar's main movie animation staff, as the animators behind the first film were working on A Bug's Life and the IPG had already proved itself by making as many frames of animation for their games as there was in the first Toy Story, with a near-identical quality. Due to the shuttering of the IPG, later Pixar PC games using pre-rendered graphics, such as A Bug's Life Activity Center and Monsters, Inc. Scream Team Training, would have significantly lower quality animation than the movies, and Toy Story would be the only Pixar film to have an Animated Storybook based on it.
In Speed Highway, several billboards can be found depicting an unknown female character. In 2020, Satoshi Okano, a former designer at Sega who worked on Sonic Adventure, revealed that this was a scrapped spider character he designed with the prototype name "Spider Girl", and posted an old sketch of the character alongside a sketch of another scrapped character, a bat named "Fly the Vampire". In 2023, Okano posted an inked version of the original Spider Girl sketch from the same time period alongside several inked sketches from the development of Samba de Amigo. Spider Girl's appearance on the billboards in Sonic Adventure suggests that the character lasted far enough into the game's development to receive a 3D model, but the character was ultimately scrapped for unknown reasons, and this 3D model has yet to surface on its own. It's unknown what role either Spider Girl or Fly were intended to have, though fans have noted that Spider Girl has some similarities to Rouge the Bat from Sonic Adventure 2, namely that both characters have large bosoms and prominent heart-based/romantic imagery.
Hugh has an unused model of a spear, referencing the popular caribou hunting chant scene from The Adventures of Jimmy Neutron: Boy Genius episode "Jimmy on Ice". While it is fully textured and loaded into the game whenever Hugh is, it is not used.
About a month before the release of Yakuza: Like a Dragon in North America, the protagonist of that game, Ichiban Kasuga, made his playable debut in the region in the game Streets of Kamurocho, a reskin of a Streets of Rage 2 level with Yakuza characters and locations. His moveset is a reskin of Axel Stone from that game as are the other two playable characters: Kazuma Kiryu and Goro Majima.
In Crash Bandicoot 4: It's About Time, the relics only appear as 2D images. However, complete 3D models can be found for all of them inside the game, including three variants of the N. Sanely Perfect relic that seem to be tiered (one being a skull, another being a skull with crossbones, and the last being a skull with crossbones; wings; horns; and a more menacing face which is closer to the final N. Sanely Perfect Relic aside from the wings), all with their own animations.
Ed, Edd n Eddy: Scam of the Century uniquely uses flat character heads on 3D bodies. However, Ed's texture contains segments from a 3D head, suggesting that the game may have originally used fully 3D characters.
Early footage of Dinosaur Planet shows that Sabre and Krystal were to utilize the Projectile spell by firing it directly from their hands. It seems this was already scrapped by the time of the December 2000 build that was leaked on the internet in early 2021, as Sabre (or Fox McCloud, who has already replaced Sabre at this point) and Krystal instead fire projectiles through their sword and staff respectively. This would carry over into Star Fox Adventures, where Fox can fire magic projectiles through Krystal's staff.
One holdover from this early idea that remains in both the December 2000 build of Dinosaur Planet and the final Star Fox Adventures is within the prologue, where Krystal, riding on top of a CloudRunner, is inexplicably shown to be able to fire blasts of magic from her own hands in the battle against General Scales' galleon.
Unused models of both Sabre and Krystal's arms can be found within the files of the leaked Dinosaur Planet ROM.
Inside the files of Wii Fit is an early model for the trainer who less resembles a mannequin and moreso appears to be distinctly white with blonde hair and almost fully realistic. The exceptions to this being her feet which have no toes, and her clothes that - while roughly the same color as the final character - are textureless (note that the attached image appears to be wearing a white onesie due to a rendering error). Based on the structure of the model and the full version of her body texture, it is apparent that the model was originally nude and the developers simply retextured parts of her body to create her clothing. The clothing meshes have their UV data removed, making them unable to use the body texture. The trainer also has a few unused animations of some warm-up stretches and yoga poses, but her shoulders get distorted and inverted due to how they are rigged. Additionally, while the warm-up poses flow together, the yoga poses (different steps of the Tree pose) are almost completely still and have no transition between them.
The European box art for Sonic 3D: Flickies' Island was not a CGI image, but rather a clay model created by Me Company, a Japanese clay studio whose in-house style involved digitizing its models and editing in elements to make them appear computer-generated.
At some point in the 2000s, a promo video was made by THQ and Toys R Us to encourage Toys R Us store owners to stock THQ video games. This tape opens with a strange, off-model rendition of SpongeBob not resembling any of his video game models and with notable details such as his pore locations, finger shape, and amount of fingers being completely off from Nickelodeon's style guide. The video also has imitation music not taken from either the SpongeBob SquarePants TV show nor any of its video games. Despite this, the video does use legitimate background art from the cartoon, and has voice work seemingly done by SpongeBob's voice actor Tom Kenny. While SpongeBob's model seems to be original, Patrick's model is taken from Nicktoons Unite!, sporting the distinctive face-long mouth and half-shut eyelids of his model used throughout the Nicktoons platformer game series. The complete promo video is not known to have been preserved.
Some of the characters during Star Fox Assault's briefing cutscenes feature details in the back that are typically unseen by the player, since the models are normally only viewed from the front. The only way around this is to move the camera using an emulator.
One such example is Beltino Toad, Slippy Toad's father. Rotating his model around reveals his coat has the logo for Space Dynamics, the manufacturer for many of the Star Fox team's vehicles, such as the Arwing, Great Fox and Landmaster.
This particular logo had actually first appeared in the official Star Fox Mission File Printout guidebook released for the original Star Fox on SNES in Japan, back in 1993.
The toothbrush model in Yandere Simulator, a background prop with no in-game use, at one point had 5,592 faces, making it the heaviest model in the game, including characters and entire interior rooms. It is theorized that the model was originally made for photorealistic CGI in commercials, and had its polygon count shoddily reduced, as each individual bristle on the brush is rendered. Eventually, the model would be replaced, giving it the much smaller - albeit still-ridiculously high - triangle count of 994.
This indicates that this was either merely a placeholder, or at some point, the development team had considered bringing the original Great Fox model back as it was prior to Assault's ending.
During any cutscene where Bayonetta has a lollipop, if you hold down a specific button before the candy head of the lollipop first appears, you will gain the effect of a specific lollipop item available in the game's stores, and this is reflected in the cutscene by changing which lollipop flavor is shown:
• A for Green Herb lollipop (recover health) • B for Bloody Rose lollipop (temporary damage boost) • X for Purple Butterfly lollipop (recover magic) • Y for Yellow Moon lollipop (gain armor)
It is pertinent that you press and hold the desired button before the candy part of the lollipop is actually seen in the cutscene to ensure the trick works. For example, in Chapter IV: The Cardinal Virtue of Fortitude, when Bayonetta walks into the colosseum, you can see that she is holding a lollipop, but you can only see the stick at first, meaning there's still time to perform the trick. If performed correctly, the lollipop head will be revealed as the one you have chosen. You can also skip the cutscene while still holding the button in order to keep the effect. Unlike normally using a lollipop item, performing this trick does not remove points from your score in a chapter.
Going off of the colors of each lollipop that are used for each face button, they match up with the Xbox 360 controller's color scheme, possibly being a remnant of Platinum Games primarily developing Bayonetta for the Xbox 360. This feature would not be carried over into subsequent Bayonetta games.
Patrick's Super move was originally going to feature a unique squashed model for each character - these were ultimately scrapped for unknown reasons, with Patrick simply slamming down his rock on the opponent without any transformations or unique animations attached.
The Landmaster's appearance as Fox, Falco and Wolf's Final Smashes in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS and Wii U is a composite of its appearances from Star Fox 64 and Star Fox Assault, maintaining the sharp and futuristic appearance it had in the latter, but still retaining traditional tank treads as seen in the former.
This particular design would eventually be implemented into the Star Fox series proper, beginning with the Landmaster's appearance in Star Fox 64 3D, and would be used again in Star Fox Zero.
Originally, going by some of the initial concept art as well as early gameplay footage for Star Fox Adventures, the tip of Krystal's staff was meant to transform whenever Fox performed one of its magic abilities. For example, when Fox performed the Ground Quake ability, it'd transform into a hammer. Curiously, one of the pieces of concept art mentions the staff transforming into a wing tip to give Fox the ability to glide, which goes unused in the final game. The models for these staff transformations were also found within the E3 2002 kiosk version of Star Fox Adventures. Ultimately, this went unused in the final game.
In Speed Highway, several billboards can be found depicting an unknown female character. In 2020, Satoshi Okano, a former designer at Sega who worked on Sonic Adventure, revealed that this was a scrapped spider character he designed with the prototype name "Spider Girl", and posted an old sketch of the character alongside a sketch of another scrapped character, a bat named "Fly the Vampire". In 2023, Okano posted an inked version of the original Spider Girl sketch from the same time period alongside several inked sketches from the development of Samba de Amigo. Spider Girl's appearance on the billboards in Sonic Adventure suggests that the character lasted far enough into the game's development to receive a 3D model, but the character was ultimately scrapped for unknown reasons, and this 3D model has yet to surface on its own. It's unknown what role either Spider Girl or Fly were intended to have, though fans have noted that Spider Girl has some similarities to Rouge the Bat from Sonic Adventure 2, namely that both characters have large bosoms and prominent heart-based/romantic imagery.
Hugh has an unused model of a spear, referencing the popular caribou hunting chant scene from The Adventures of Jimmy Neutron: Boy Genius episode "Jimmy on Ice". While it is fully textured and loaded into the game whenever Hugh is, it is not used.
In the files of Chicken Run, there is an unused model for Edwina, a character who dies and gets eaten early into the movie.
In Crash Bandicoot 4: It's About Time, the relics only appear as 2D images. However, complete 3D models can be found for all of them inside the game, including three variants of the N. Sanely Perfect relic that seem to be tiered (one being a skull, another being a skull with crossbones, and the last being a skull with crossbones; wings; horns; and a more menacing face which is closer to the final N. Sanely Perfect Relic aside from the wings), all with their own animations.
Ed, Edd n Eddy: Scam of the Century uniquely uses flat character heads on 3D bodies. However, Ed's texture contains segments from a 3D head, suggesting that the game may have originally used fully 3D characters.
The Utah Teapot, a 3D graphics in-joke, can be found in the data of Watch Dogs 2 as an unused vehicle.
Early footage of Dinosaur Planet shows that Sabre and Krystal were to utilize the Projectile spell by firing it directly from their hands. It seems this was already scrapped by the time of the December 2000 build that was leaked on the internet in early 2021, as Sabre (or Fox McCloud, who has already replaced Sabre at this point) and Krystal instead fire projectiles through their sword and staff respectively. This would carry over into Star Fox Adventures, where Fox can fire magic projectiles through Krystal's staff. 
Inside the files of Wii Fit is an early model for the trainer who less resembles a mannequin and moreso appears to be distinctly white with blonde hair and almost fully realistic. The exceptions to this being her feet which have no toes, and her clothes that - while roughly the same color as the final character - are textureless (note that the attached image appears to be wearing a white onesie due to a rendering error). Based on the structure of the model and the full version of her body texture, it is apparent that the model was originally nude and the developers simply retextured parts of her body to create her clothing. The clothing meshes have their UV data removed, making them unable to use the body texture. The trainer also has a few unused animations of some warm-up stretches and yoga poses, but her shoulders get distorted and inverted due to how they are rigged. Additionally, while the warm-up poses flow together, the yoga poses (different steps of the Tree pose) are almost completely still and have no transition between them.
The European box art for Sonic 3D: Flickies' Island was not a CGI image, but rather a clay model created by Me Company, a Japanese clay studio whose in-house style involved digitizing its models and editing in elements to make them appear computer-generated.
At some point in the 2000s, a promo video was made by THQ and Toys R Us to encourage Toys R Us store owners to stock THQ video games. This tape opens with a strange, off-model rendition of SpongeBob not resembling any of his video game models and with notable details such as his pore locations, finger shape, and amount of fingers being completely off from Nickelodeon's style guide. The video also has imitation music not taken from either the SpongeBob SquarePants TV show nor any of its video games. Despite this, the video does use legitimate background art from the cartoon, and has voice work seemingly done by SpongeBob's voice actor Tom Kenny. While SpongeBob's model seems to be original, Patrick's model is taken from Nicktoons Unite!, sporting the distinctive face-long mouth and half-shut eyelids of his model used throughout the Nicktoons platformer game series. The complete promo video is not known to have been preserved.
Some of the characters during Star Fox Assault's briefing cutscenes feature details in the back that are typically unseen by the player, since the models are normally only viewed from the front. The only way around this is to move the camera using an emulator.
Unusued icons found within Star Fox Command curiously show ROB 64 with the original Great Fox as it appeared in previous installments such as Star Fox 64 and Star Fox: Assault. This is odd, because the Great Fox was already shown to be completely destroyed in the climax for the previous game, Star Fox: Assault, which is why it was replaced with a small space carrier in the final version of Command. 
During any cutscene where Bayonetta has a lollipop, if you hold down a specific button before the candy head of the lollipop first appears, you will gain the effect of a specific lollipop item available in the game's stores, and this is reflected in the cutscene by changing which lollipop flavor is shown:
Patrick's Super move was originally going to feature a unique squashed model for each character - these were ultimately scrapped for unknown reasons, with Patrick simply slamming down his rock on the opponent without any transformations or unique animations attached.
The Landmaster's appearance as Fox, Falco and Wolf's Final Smashes in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS and Wii U is a composite of its appearances from Star Fox 64 and Star Fox Assault, maintaining the sharp and futuristic appearance it had in the latter, but still retaining traditional tank treads as seen in the former.