In Chapter 4, the piano in the first sanctuary allows for a much more expansive range of notes than other in-game pianos. Accordingly, Susie and Ralsei have special reactions if the player inputs specific songs on it:

• Playing "Memory" results in Ralsei complementing it by comparing it to a lullaby.
• Playing "Your Best Friend" from Undertale results in Ralsei calling it "friendly and sweet," alluding to Flowey's introductory cutscene in that game.
• Playing "The Legend" flatters Ralsei, to which Susie responds by joking that Kris is flirting with him.
• Playing "Lost Girl" results in Susie wondering if she could learn it on guitar.
• Playing "Rouxls Kaard" results in Ralsei recognizing it as Rouxls' theme song; Susie then jokingly calls it the "theme of him getting his ass kicked."
• Playing "Heartache" (Toriel's boss theme in Undertale) causes Ralsei to describe it as "emotional" before Susie suggests playing it for Toriel.
• Playing "Undertale" results in Susie deriding the song as "crap."
• Playing "Dark Sanctuary" results in Susie pointing out that "Ralsei was humming it earlier."
• Playing the song on the Old Man's sheet music results in different responses depending on whether or not the player includes the octave switch: omitting it results in Susie & Ralsei commenting on its absence, while including it results in Susie commenting on how different it is.
• Playing the first four notes of "MEGALOVANIA" (Sans' boss theme from Undertale) results in the Annoying Dog abruptly running Kris over with the car from Cyber City's hidden alley in Chapter 2, which causes a smash to black before the game returns to normal. Attempting to replay the song results in Kris fumbling the fourth note.

Several other songs that produce reactions are transcribed unusually, and as such are more difficult to trigger if playing solely by ear:

• Playing A, D, E, F, D, D, C, D, B, A, D, E, D, C, D, D causes the pair to comment on the "annoying" nature of the melody.
• Playing "Don't Forget" (C, D, E, E, E, E, E, A, C, B, B, B, B, B, B, C, B, A, A, A, A, A, A, G, H, G, E, C) causes Susie to fall silent before calling the song "kinda cool."
• Playing "Spear of Justice" (E, D, B, C, A, B) results in Susie calling the song "majestic" before Ralsei suggests that the Old Man would enjoy it, referencing the song's nature as Spoiler:both Undyne and Gerson's leitmotif.
• Playing "Chopsticks" by Euphemia Allan, "Heart and Soul" by Frank Loesser & Hoagy Carmichael, or "You've Got a Friend in Me" by Randy Newman & Lyle Lovett (C, E, C, F, E, A, F, H, F, H, E) results in Susie scolding Kris for "messing around." Notably, all three of these are real-life, commercially released songs: the first two are common stock piano pieces, while the latter was recorded for the 1995 animated film Toy Story. Its inclusion likely references a series of comedic edits of the song posted to Tumblr by developer Toby Fox. One of these edits, "Friend inside Me", was previously the subject of tongue-in-cheek fan theories claiming that it would pertain to Chapter 3's hidden boss.

Eight games developed by Rare for the Game Boy Color and Game Boy Advance feature a recurring Easter egg: a crude drawing of a bovine eating a flower. Dubbed the "Rare Cow", it made its first known appearance in Conker's Pocket Tales in 1998, and last appeared in It's Mr. Pants in 2004.

The design of the Angels in the PlayStation version of the game was inspired by the clothes worn by Milla Jovovich's character Leelo in the 1997 film The Fifth Element. The costume designs for the film were done by French designer Jean Paul Gaultier, who Shin Megami Tensei demon designer Kazuma Kaneko and SaGa series illustrator Tomomi Kobayashi had previously expressed admiration for.

Each version of the game has a costume called the Launcher with a themed design unique to each console, though all variants of them perform the same ability of shooting bullets while standing still:

• Star Launcher is exclusive to the Nintendo Switch version and is red akin to the Nintendo logo. Its bullets feature star effects, likely in reference to the Mario series.
• Blue Launcher is exclusive to the PlayStation 4 and PlayStation 5 versions and visually resembles a PS5 console. Its bullets feature effects with the PlayStation face button symbols.
• X Launcher is exclusive to the Xbox One and Xbox Series X|S versions and prominently features the Xbox logo. Its bullets feature green X's similar to the Xbox logo.
• Steam Launcher is exclusive to the PC/Windows version and features a large red valve on its back, in reference to Steam's creator Valve. Its bullets are also valve shaped.

Each version's Launcher costume was originally unlocked if save data from the game's demo was detected, but since the demo is no longer downloadable, the costumes can now only be unlocked by inputting a specific code on the title screen: L, R, L, R, L, L, R, R, Up, Down. The official Balan Wonderworld Twitter account initially posted a hint for players to figure out the code themselves, which could be solved by identifying which costume is found in the applicable world number.

The SNES version of Mortal Kombat was developed by Sculptured Software in the conservative state of Utah, an area where the backlash to the game's violent content was at its highest, and whose state legislature previously attempted to outlaw the original arcade version. According to the port's project director Jeff Peters, local children visiting the studio to ask about the game and its development also told their parents, who refused to associate with the developers and speculated that they were "drug dealers" and "Satan worshippers". He also recalled one programmer who asked the development team to lie to his family about what game he was working on.

On October 26, 2024, a special demo version of the game was given exclusively to YouTuber Matthew Patrick and livestreamed on his channel GTLive before he officially retired from making YouTube videos on that day. The end of the demo featured a special ending set within the Nugget Cave, referencing various theories and moments related to the series that Patrick covered on his webseries "Game Theory". Nugget then appears and declares him and his wife Stephanie Cordato to be "true friends of Nugget" while a sign saying "Farewell Matpat!" descends amongst a downpour of chicken nuggets.

The inclusion of the character Pauline was accidentally leaked through a piece of thumbnail artwork on Nintendo of Korea's website shortly after the game's announcement, but was quickly removed. Her inclusion would later be confirmed in a dedicated Nintendo Direct aired on June 18, 2025, where it was revealed that she was Spoiler:the true identity of the character Odd Rock.

On May 28, 2025, voice actor Yuri Lowenthal, who voiced Yosuke in the English dub of the original game, posted a live performance of the song "Oh No" by the American punk rock band Gogol Bordello to his Bluesky account. Three minutes later, Lowenthal leaked the existence of the game's unannounced remake in a second post. When combined, both posts read as:


Lowenthal previously voiced Eichiiro in Persona 3 Reload after that game's protagonist was recast. In response to fan questions stemming from this announcement, voice actresses Erin Fitzgerald and Amanda Winn Lee also confirmed that they would not be returning as Chie and Yukiko respectively. Considering Lowenthal was participating in the 2024-2025 SAG-AFTRA video game voice actor strike, the nature of both posts being made so close to each other could have been related to that. He deleted his second post days prior to the game's announcement at the Xbox Games Showcase on June 8. Coincidentally, all three actors revealed they would not be in the game in the order their characters join the party in the original game. Earlier in March, in response to a Japanese web domain for the remake being registered, Johnny Yong Bosch revealed that he was open to reprising his role as Yu and to the possibility that he might get replaced.

In 2011, an article was added to the website Unseen64 describing a cancelled Xbox game based on the children's television series The Big Comfy Couch, including screenshots of what appeared to be bloody combat against sinister versions of the Dust Bunnies from the show. Unseen64 claimed that they had verified the screenshots and that they were provided by a developer who had also given them images of an unreleased Power Rangers game, Power Rangers Legacy, running on the same proprietary engine. Users on the Lost Media Wiki in their attempts to search for more information found a possible lead named Chris Tang, a former Capcom developer who worked on both games while working at GenAzea, an independent studio co-founded by fellow Capcom alumn Erik Suzuki. As it turned out, Suzuki was the first husband of Alyson Court, the actress who portrayed the show's protagonist Loonette the Clown and was the original English voice of Claire Redfield in the Resident Evil series. When asked, she confirmed the game existed and that it was cancelled when its developer shut down; GenAzea has since relaunched under the name HitSparks Games. After a user on the wiki contacted Tang in 2021, he visited their Discord server and provided various screenshots and video footage, as well as images of a cancelled Capcom game in the same engine, Capcom Generations. He also clarified that the blood was placeholder "grape juice".

While hovering over Yoshi or any of his outfit variations on the character select screen in any mode, there is a chance that he will hum Totaka's Song, a short melody written by veteran Nintendo composer and Yoshi voice actor Kazumi Totaka that has been inserted into most of the games he worked on. Although Totaka was not part of the music team for Mario Kart World, he is credited for reprising his role as Yoshi.

The designs of the passive item Infamy and the boss Mask of Infamy are a reference to Carmilla from Castlevania II: Simon's Quest.

Within the data for Chapter 4 are unused sprites depicting Susie playing a handheld video game while hanging out with Noelle. Concept art for this was shown off in a tweet by Toby Fox in 2022, alongside artwork of two other character interactions. Notably, the Susie and Noelle scenario is the only one shown in the tweet that isn't featured in the final game.

In Spoiler:the Weird Route version of Chapter 4, one pivotal scene depicts Spoiler:Kris, possessed by the SOUL, forcing Noelle to re-don the Thorn Ring from Chapter 2 by slowly creeping towards her as she backs away in fear across a couch. In the original release of the chapter, this gives way to an animation Spoiler:of a rose blooming and then crumbling against a black screen, located in the same place as Noelle's sprite. In the Version 1.01A update, this was replaced by Spoiler:a single red pixel, possibly as a placeholder graphic, which in turn was replaced in Version 1.01C with another animation depicting cracking red glass. The original animation is outright removed from the game's files in these later updates rather than being merely disabled.

The reason for this alteration was not explained in the official changelogs, which respectively described the changes as a "Small graphical alteration to a certain scene" and "Strengthened imagery while maintaining a scene's intended meaning". The original animation was likely changed in response to complaints from players who interpreted it as Spoiler:Noelle being forcibly "deflowered" (taking her virginity, in this case through rape) literally, in addition to being driven insane, and to counter-complaints Spoiler:lamenting the reduced emotional impact when the single red pixel was implemented. Spoiler:The couch sequence moments prior remained unchanged with each update, making it unknown if Spoiler:the rape implication was intended, presumably metaphorically, in all versions of the scene.

At 12:00 Noon every day, Lord British, who was modelled after series creator Richard Garriott, will leave his throne room and walk out to its doorway, with a gold plaque hanging over it that reads "The Throne Room of Lord British". If you click on this plaque when he is directly underneath it, it will fall on his head and kill him. Afterwards, one of the party members will declare: "He's dead, Avatar! Yancey-Hausman will pay!" This quote and the way he is killed are a reference to an incident that occurred during the game's development. While checking on some employees during a smoke break, Garriott was struck by a large 8-pound magnet that fell from a security door in Origin Systems' offices, and he was hospitalized with a concussion. Yancey-Hausman was a Texan real estate firm who owned the offices at the time. Before showing the finished Easter egg to Garriott, the development team gifted him a hard hat adorned with a picture of a goose saying "Ankh Ankh", a pun referencing the recurring symbol in the Ultima series.

According to Larian Studios CEO Swen Vincke, Ultima VII: The Black Gate is his favorite RPG, and it had a life-long influence on the development of the Divinity series and Baldur's Gate 3. Amidst the increasing popularity of the Diablo series, he felt that he needed to carry the baton for the environmental interactivity, non-linear gameplay, and dialogue/party reactions featured in Ultima VII that had otherwise been neglected or abandoned in other RPGs at the time.

In October 2020, a Facebook account known as "Leftist Gamer Memes" posted a meme depicting Wiefgraf saying left-wing rhetoric in a similar vein to the anti-capitalist themes in Final Fantasy Tactics:


This meme would be shared so much that other users and internet sources began to mistakenly cite it as a real quote from the game. The game's writer and director Yasumi Matsuno eventually discovered the meme and clarified it was a fake quote, but nonetheless saw it as "something I would have written." He felt the meme's appeal stemmed from people dropping the game after its first chapter and not fully seeing the rest of Wiefgraf's character, stating:

In the game files, some debuting characters and arenas are referred to with their internal production names:

• The Falling Cliffs stage is named "kollapsing_kliffs"
• The Nethership Interior stage is named "netherbelly"
• Havik is named "skab"
• Shujinko is named "monk"
• Monster is named "freak"
• Darrius is named "cassius"

There are three unused Announcer voice clips found in the game's code, one of which announces the name of the non-playable sub-boss Moloch. This was found grouped with character selection screen data, suggesting that he was once planned to be included as an unlockable playable character. There are also two humorous voice clips shouting "Fat!" and "Fantastico!" that may have been recorded as inside jokes, but their intended purpose remains unknown.