After killing the Swirl in mid-flight, a black vertical line appears across the spot where the Swirl was shot. This line is referred to under the Helpful Hints section in the game's manual as the "Ghost of Yars" and warns the player to stay off its "mean streak". If the Yar is in the lower third of the screen and the black spot on its back is aligned across the vertical line at the moment the explosion vanishes, the game ends and goes into the "Game Select" screen with "HSWWSH" in place of the player's score. These are the mirrored initials of the game's creator Howard Scott Warshaw.
Located on the rooftop of Tom's Diner (over at Bradbury & Buran) is a pair of binoculars. If the players uses the binoculars to look up to the left, they'll find graffiti of the Northern cardinal bird that's used in CD Projekt RED's logo. After waiting a few moments, the vision in the binoculars will glitch and shift to show a picture of the game's dev team superimposed over the screen. According to global community director Marcin Momot and senior PR manager Marta Piwońska, this picture was taken at an annual company picnic on CD Projekt RED's 20th anniversary in 2022.
In King Nnyere's office in his Fort in Lebao-Sako, there is a side table with assorted bottles of liquor, including a unique bottle that can only be found in the Fort. It is a bottle of Extra Special, 43% volume Old French Whisky bottled in Quebec and aged for 30 years, and its label features the face of its brand name "Thomas Gillet: Polack Connection". Gillet was a texture artist at Ubisoft Quebec at the time, but he is not known to have worked on Far Cry 2. The bottle of French whiskey being produced in Quebec is a nod to Ubisoft Quebec, while the name "Polack Connection" seems to both be a nod to the 1971 film "The French Connection" and possibly Gillet's heritage. It's unknown if or how the remaining bottling details relate to Gillet.
Gameplay (there is no close zoom-in on the bottle in this footage so the texture is blurry, but "Polack Connection" can be made out on it, and it's the closest look at the bottle on video available at the moment): https://www.youtube.com/watch?v=p-0fNhHuesk#t=430
If you enters password PROGRESS and then the cheat code A, Right, Down, B, Left, Up, B, B, A in Spot Goes to Hollywood's pause screen, you will unlock a minigame called FRUITMEISTER 2, a slot machine game using developers' heads. There is no reward for winning the game (something cheekily acknowledged in-game with the caption "win a prize or something - probably"). A first FRUITMEISTER minigame is not currently known to exist in any other Eurocom game.
The Game Gear and Master System version of Daffy Duck in Hollywood has a set of 3 cheat codes - the first 2 being a stage select code and an invincibility code. If you enter those in that order and then the third code, Daffy's sprite will be replaced with a digitized image of Probe founder Fergus McGovern.
If you fly up to the height at which the ship spawns while protecting a human in Wave 25 of the Atari 2600 version of Defender, all enemy ships will transform into the letters "BP", standing for Defender creator Bob Polaro.
The Official Star Fox Missile File Printout guidebook released alongside the original Star Fox on SNES in Japan mentions two pilots, Desla Koba and Bear Noguccini, who don't appear anywhere in the game proper. They were said to be two of the most capable members in the Cornerian Defense Force, who had previously embarked in cutting-edge Arwing scouting vessels.
Both were said to have mysteriously disappeared. It is said later on in the guidebook that Desla Koba had disappeared in the Asteroid Belt when he came across a mysterious giant space bird, and upon trying to inspect it, he ended up being warped into another dimension, known in-game as "Out of this Dimension". Similarly, Bear was last seen in Sector Y, where he encountered the mysterious space whale before losing all contact, never to be seen again.
Desla Koba would actually be mentioned again in Star Fox 64's official Japanese guidebook, with a similar backstory that he had in the Missile File Printout guidebook. Here, it is said that he led a unit conducting an investigation in Meteo (SF64's equivalent to the Asteroid Belt from SF1), only for communications to suddenly be cut off as he'd apparently entered the stage's warp zone, which simultaneously led to him crashing his aircraft on the nearby planet of Katina. This was said to have occurred more than 10 years prior to the events of Star Fox 64.
Both Desla Koba and Bear Noguccini's surnames seem to come from two of the editors of the Mission File Printout guidebook: Hitoshi Kobayashi and Yukata Noguchi.
In the Easter egg "Developer's Grove" area that is unlocked upon donating 10,000 Rapo-Coins to the Wishing Well, one of the developers will inform the player that there is a "secret flower" hidden in the game that can bring the Mayor, who dies in the final world, back from the dead - while another developer tells the player that the other developer is lying. There is no secret flower.
In the SNES version of Mario's Early Years! Fun with Letters, there is an Easter egg where, after clicking a very specific pixel on the ground in the bedroom, three developers will appear in the window and say hello.
If you press 3 on the right controller while the gorilla is falling off of the skyscraper, the initials "WB", standing for programmer Wendell Brown, will appear on the building.
If you name your players in the NES version of MTV Remote Control "PLEASE", "SHOW", and "RSP" (RSP standing for the game's developers, Riedel Software Productions) and then press start, you will be able to see pictures of programmer Mike Riedel, sprite artist Remington Emin, and assistant programmer Eric Shefferman, 3 of the game's 4-person developer team (with the missing 4th developer being composer Nick Scarim). If you press A or B, they'll smile at you.
After recruiting Hugo, you can give him your Old Books and read them in the Castle's library on the third floor. In the Japanese version of the game, while reading these books, dataminers years ago found that a seemingly unused crudely-drawn sketch of the game's cover artwork was loaded into the VRAM. In reality, this sketch was not unused, but was actually part of an obscure Easter egg: a secret 9th Old Book. While highlighting the 8th Old Book titled "The Kalekka Incident", press Square, Circle, Triangle, and Cross at the same time. This will unlock the hidden 9th volume entitled "Hirotaka Development Diary" (presumably referring to the game's producer Hirotaka Ishikawa). A very rough English translation of the book's first four pages can be seen below:
- Pages 1 & 2 - (About the library)
"The Game Master used a ”Please/Favor Card”.
Thus my daily assistance began.
July 10th (Mon)
Made the BG graphics.
July 11th (Tue)
Made the page graphics.
July 12th (Wed)
Entered the text.
- Pages 3 & 4 - (About the mural)
The Game Master gave me the next job.
July 13th (Thu)
Made the images for the pieces.
Didn't have time so had to finish in one day.
(About the Stone Monument)
July 17th (Mon) – July 21st (Fri)
It was difficult because it doesn't have a face.
(About the Bath)
July 24th (Mon) – July 29th (Sat)
I want to have a bath too!"
The last two pages of the developer diary featured the crude sketch of the game's cover art alongside a request to mail in your opinions on the game to a listed address that is presumably somewhere in Kanda-Jinbōchō in Tokyo (Note: this full page has not been translated). It's not known if this secret is in the Sega Saturn version of the game, but it is confirmed to work on the PlayStation Portable port, Genso Suikoden I & II. However, this port has the last two pages (including the sketch of the cover art and request for opinions) removed, reducing it to four pages instead of six.
In the Japanese version of Alex Kidd in Miracle World, there is a heartfelt secret message accessible by holding Button 1 on controller 2, and then Button 2 or 1 on controller 1 on the ending screen:
"We dedicate this story to Kōichi and Emi. May children yet to be born be strong, and have love and bravery like Alex. And we, together with Alex, hope that all who love him may be forever happy. By: Kōtarō Yōko Matilda Rie Wakashimazu Papa Kōichi Toku Kaori the Bully Toshi the Bullied"
In the Police Headquarters, when Sly opens the vault containing his police file, you can see a bottle on top of the vault with a label reading "HOKYO". This is a reference to Hokyo Lim, a concept artist who worked on the first three games in the series.
In the Blood and Wine expansion, you cannot access Mount Gorgon in Toussaint by normal means. However, there is a small grassy field on the summit of the mountain that can be accessed using mods. If you teleport Geralt there, you can find a blank canvas with a red blotch on it sitting in-between two columns. Using Witcher Sense to view the canvas will reveal a completed painting: a group picture of the game's developers at CDProjekt Red.
On the main menu, if you drag the galaxy and spin it around long enough, four pictures of the game's developers will fly out of the galaxy. However, if you do this while pressing Ctrl+Shift, even more developer pictures will appear.
During the "Scorched Earth" campaign mission in Berlin, hidden in an alcove immediately to the left after walking into the Trivo Buchhandlung ("Trivo Bookstore" in German) are a shelf and display of books adorned with the names of numerous developers who worked on the game. The most notable kind of book in the display however features the name Guy Beahm and a black and red circle with a pair of sunglasses and a moustache. Beahm is better known by his online alias Dr. DisRespect since 2010, a character known for his over-the-top personality and appearance, including the same sunglasses and moustache that appear on the book cover. Beahm was hired by Sledgehammer Games as a Community Manager in 2011, and the following year accepted a Level Designer position in the studio where he designed multiplayer maps for Modern Warfare 3 and Call of Duty: Advanced Warfare. Beahm left Sledgehammer in 2015; this Easter egg went largely unnoticed until 2022.
In the game's data, found at the offset 0x32E of it's ROM are the strings "MINATO", referencing Minato Giken, the developer company that worked on the game.
The ending of Half-Life: Decay can be seen from the perspectives of either playable character in the game, Gina or Colette. If you see the ending from Colette's perspective, a brief shot of a broken computer can be seen with red electrical arcs shooting out of it. Connecting these arcs in an emulator reveals the initials "MA", the signature of Gearbox Software level designer Matt Armstrong, and a symbol that he would often hide in games he worked on.
Located on the rooftop of Tom's Diner (over at Bradbury & Buran) is a pair of binoculars. If the players uses the binoculars to look up to the left, they'll find graffiti of the Northern cardinal bird that's used in CD Projekt RED's logo. After waiting a few moments, the vision in the binoculars will glitch and shift to show a picture of the game's dev team superimposed over the screen. According to global community director Marcin Momot and senior PR manager Marta Piwońska, this picture was taken at an annual company picnic on CD Projekt RED's 20th anniversary in 2022.
In King Nnyere's office in his Fort in Lebao-Sako, there is a side table with assorted bottles of liquor, including a unique bottle that can only be found in the Fort. It is a bottle of Extra Special, 43% volume Old French Whisky bottled in Quebec and aged for 30 years, and its label features the face of its brand name "Thomas Gillet: Polack Connection". Gillet was a texture artist at Ubisoft Quebec at the time, but he is not known to have worked on Far Cry 2. The bottle of French whiskey being produced in Quebec is a nod to Ubisoft Quebec, while the name "Polack Connection" seems to both be a nod to the 1971 film "The French Connection" and possibly Gillet's heritage. It's unknown if or how the remaining bottling details relate to Gillet.
If you enters password PROGRESS and then the cheat code A, Right, Down, B, Left, Up, B, B, A in Spot Goes to Hollywood's pause screen, you will unlock a minigame called FRUITMEISTER 2, a slot machine game using developers' heads. There is no reward for winning the game (something cheekily acknowledged in-game with the caption "win a prize or something - probably"). A first FRUITMEISTER minigame is not currently known to exist in any other Eurocom game.
The Game Gear and Master System version of Daffy Duck in Hollywood has a set of 3 cheat codes - the first 2 being a stage select code and an invincibility code. If you enter those in that order and then the third code, Daffy's sprite will be replaced with a digitized image of Probe founder Fergus McGovern.
If you fly up to the height at which the ship spawns while protecting a human in Wave 25 of the Atari 2600 version of Defender, all enemy ships will transform into the letters "BP", standing for Defender creator Bob Polaro.
The Official Star Fox Missile File Printout guidebook released alongside the original Star Fox on SNES in Japan mentions two pilots, Desla Koba and Bear Noguccini, who don't appear anywhere in the game proper. They were said to be two of the most capable members in the Cornerian Defense Force, who had previously embarked in cutting-edge Arwing scouting vessels. 
In the SNES version of Mario's Early Years! Fun with Letters, there is an Easter egg where, after clicking a very specific pixel on the ground in the bedroom, three developers will appear in the window and say hello.
If you press 3 on the right controller while the gorilla is falling off of the skyscraper, the initials "WB", standing for programmer Wendell Brown, will appear on the building.
If you name your players in the NES version of MTV Remote Control "PLEASE", "SHOW", and "RSP" (RSP standing for the game's developers, Riedel Software Productions) and then press start, you will be able to see pictures of programmer Mike Riedel, sprite artist Remington Emin, and assistant programmer Eric Shefferman, 3 of the game's 4-person developer team (with the missing 4th developer being composer Nick Scarim). If you press A or B, they'll smile at you.
After recruiting Hugo, you can give him your Old Books and read them in the Castle's library on the third floor. In the Japanese version of the game, while reading these books, dataminers years ago found that a seemingly unused crudely-drawn sketch of the game's cover artwork was loaded into the VRAM. In reality, this sketch was not unused, but was actually part of an obscure Easter egg: a secret 9th Old Book. While highlighting the 8th Old Book titled "The Kalekka Incident", press Square, Circle, Triangle, and Cross at the same time. This will unlock the hidden 9th volume entitled "Hirotaka Development Diary" (presumably referring to the game's producer Hirotaka Ishikawa). A very rough English translation of the book's first four pages can be seen below:
In the Police Headquarters, when Sly opens the vault containing his police file, you can see a bottle on top of the vault with a label reading "HOKYO". This is a reference to Hokyo Lim, a concept artist who worked on the first three games in the series.
In the Blood and Wine expansion, you cannot access Mount Gorgon in Toussaint by normal means. However, there is a small grassy field on the summit of the mountain that can be accessed using mods. If you teleport Geralt there, you can find a blank canvas with a red blotch on it sitting in-between two columns. Using Witcher Sense to view the canvas will reveal a completed painting: a group picture of the game's developers at CDProjekt Red.
On the main menu, if you drag the galaxy and spin it around long enough, four pictures of the game's developers will fly out of the galaxy. However, if you do this while pressing Ctrl+Shift, even more developer pictures will appear.
During the "Scorched Earth" campaign mission in Berlin, hidden in an alcove immediately to the left after walking into the Trivo Buchhandlung ("Trivo Bookstore" in German) are a shelf and display of books adorned with the names of numerous developers who worked on the game. The most notable kind of book in the display however features the name Guy Beahm and a black and red circle with a pair of sunglasses and a moustache. Beahm is better known by his online alias Dr. DisRespect since 2010, a character known for his over-the-top personality and appearance, including the same sunglasses and moustache that appear on the book cover. Beahm was hired by Sledgehammer Games as a Community Manager in 2011, and the following year accepted a Level Designer position in the studio where he designed multiplayer maps for Modern Warfare 3 and Call of Duty: Advanced Warfare. Beahm left Sledgehammer in 2015; this Easter egg went largely unnoticed until 2022.
The ending of Half-Life: Decay can be seen from the perspectives of either playable character in the game, Gina or Colette. If you see the ending from Colette's perspective, a brief shot of a broken computer can be seen with red electrical arcs shooting out of it. Connecting these arcs in an emulator reveals the initials "MA", the signature of Gearbox Software level designer Matt Armstrong, and a symbol that he would often hide in games he worked on.