An Easter Egg is an intentional hidden message, joke, or special feature within a computer program.
In games, easter eggs are often internal jokes related to the game's designers or references to other games developed by them. Some jokes are related to the games' fan communities or tendencies among players (such as rocket jumping).
There are several easter eggs in the Quake games and their expansions or mission packs. They are hidden and players will rarely stumble upon them by accident. To reveal them, players often have to do something unusual.
Hidden Message Near Nightmare Portal
Shooting the decoration near the Nightmare selection portal will display a secret message. It's meant as both a hint and notice to people who have played the Beta on remembering that the Well of Wishes used to be located in the Introduction.
The Well of Wishes and Dopefish
In the Crypt of Decay is a unique hidden area, in which the mythical Dopefish dwells. The place's name, as well as the textures used in it, are references to id Software's earliest game series - Commander Keen. The Well of Wishes is a special underwater level in Commander Keen 4: Secret of the Oracle.
The Initials Chamber
Shooting all the gargoyle heads in the Underearth will allow the player access to a hidden room from a corridor with flashing lights. Inside are the initals of Tim Willits and his sister, Theresa Chasar, as well as the logo from a Doom.WAD series they created together - Raven.
Quake Mission Pack 1: Scourge of Armagon
A Bonus for the Rocket Jumpers
In the main bronze machinery of the Lost Mine, there is a top of the pinnacle rock. This area is not counted as a secret and appears to be unreachable - except by rocket jumping whilst using a Quad Damage, which was already known and in use among players at the time of Scourge of Armagon's release. Reaching this higher area will reward the player with the message: "You cheatin' heart!"
Another Bonus for the Rocket Jumpers
At the very start of the Research Facility, there is a Yellow Armor on the top of the slanted wall structure. This area is not counted as a secret and appears to be unreachable - except by rocket jumping, which was already known and in use among players at the time of Scourge of Armagon's release. Reaching this area will reward the player with the message: "...thought you'd get up here somehow."
In the main chamber of the Black Cathedral is a large Crucifix on the wall, similar to the ones seen in the original Quake. This one, however, holds a deadly secret - shooting its head will unleash divine wrath on the player, in the form of a deadly lightning bolt. This can be used to the player's advantage too, as the bolts will sometimes target any monsters in the room.
Normally, the player wouldn't be able to see the top side of the three tombstones in one of The Crypt's secret areas. Using noclip (or a well-placed rocket jump), you can discover that there are some glowing red initials on top of each tombstone - SM, GB, and SB. These refer to Richard "Levelord" Gray's favorite comedians - George Burns, Steve Martin, and Shorty Berstien. However, in the enhanced version these initials have been removed.
The Levelord Giggles
The Levelord's Warning
If you discover and follow the alternative path to the tower in Tur Torment (instead of the tram), once you reach the highest point, the Levelord (i.e. Richard Gray) will warn you that "You're not supposed to be here!" Afterward, a few Spike Mines will spawn and attack you. This message mirrors several similar ones in Duke Nukem 3D, hidden across level areas that are only accessible if the player uses the noclip cheat.
A special secret area (described as "THE Secret Area" when found) in The Gauntlet holds a large sculpture that is meant to represent Hipnotic Software's logo. Shooting the button on the ceiling will cause the logo to spin, making a further allusion to hypnosis.
Quake Mission Pack 2: Dissolution of Eternity
On some bookshelves, there is a book with the face on its cover. It looks just like the Necronomicon as it appears in the Evil Dead series of horror movies. The Necronomicon, also known as the Book of the Dead, is an important element in the writings of H. P. Lovecraft, which serves as the primary inspiration for Quake and its mission packs.
The Unholy Division of Life
Hidden within an inaccessible chamber of Wizard's Keep is a shootable plate. If enough firepower is applied to it, the plate disappears, revealing a set of four rune-like letters (most likely developer initials) and displays the message "The Unholy Division of Life".
One of the iconic images at Wizard's Keep will smite the player with divine wrath, if the puny mortal dares defile it (by shooting it). The lightning bolts emerge from the icon's eyes and never miss their target. The player will also receive a warning not to defy God.
Creepy Rubber Duck
The main feature of the Lost Station in Unit 1 is the tram car that travels between the level's upper and lower section. If you board the tram, and ride it 13 times without interruption, a sign on the wall of one of the tram stations will reveal a rather creepy-looking rubber duck.
Tim Willits' Drop Pod
"Design is Law" or The Return of Dopefish
After the Strogg reactor has been destroyed and the way to Unit 7 has been revealed, return to the Cooling Factory and go back to the large outdoor area with several water pools (it is just after the large pump-like structure). A new passage will be open underwater, leading to a room with a cracked pipe. Shoot the pipe and you will encounter Dopefish yet again. The message "Design is law" is a joke on John Romero, Tom Hall, and their company Ion Storm.
Hidden Message in the Labs
Killing all human captives in the Research Lab of Unit 8, will cause the window near the level's start to change (the words "Kill Me" will appear on it, written in blood). Shoot the window and it will break. Follow the crawlspace to a hidden room, where you will receive this strange message - "A.H.D.S.S.I.B.H. - bjjc". The message's meaning is "A Hall Displays Secret Snapshots In Boss' House - Brandon James & John Carmack" - it's a hint about the hidden id Gallery in the final level.
"You Crazy Rocket Jumpers"
Rocket jumping is a popular player tactic that was not discovered until after Quake's release. This allowed certain levels to be played in unintended ways and added an entire new dimension to multiplayer. As a nod to players, there is a secret message displayed when players get on top of the closed hangar doors in the Launch Command level. The only way to get there is, in fact, a rocket jump.
The id Software Memorabilia Room
Somewhere in the lower reaches of the Upper Palace in Unit 9, is a room containing some id Software-related stuff - a Doom poster, a poster showing John Carmack's new Ferrari, as well as a locked water tank with an Ancient Head inside.
The id Gallery
After defeating the Makron in the final level, a wall in the resupply area beneath the arena will be cracked. Shoot the wall and it will break. Beyond it is a gallery dedicated to the id Software team that worked on Quake 2. Some of the developers have photos, others don't. In front of some of the photos are buttons that will produce some special effect when pressed.
The Hidden Throne Room
Pressing all the effect-generating buttons in the id Gallery mentioned above will cause a hole to appear in the floor next to Tim Willits' photo. This new passage leads to a hidden throne room, where a Tank is enjoying the company of two very naughty Iron Maidens. Some players speculate that Tank Jr. is the product of this unusual relationship.
Quake 2 Mission Pack: The Reckoning
On the level Industrial Facility, go to the exit that leads to the Refinery. Rocket jump above the door, and then again onto the ledge that should be right next to you. If you look around you will see an Invulnerability farther down the ledge. When you get close enough to it, it will disappear and the message "No prize for you, Rocketman" will appear.
Quake 2 Mission Pack: Ground Zero
Hidden Personal Message
Revealing this egg requires a considerable waste of ammo, so it would be wise to save your game first. In the first room of the Ammo Depot in Unit 4, look up and you will see a grate on the ceiling. Shoot it until it is destroyed and the message "You've found a DuNgA!" will appear. Behind the grate is a shootable button. Shoot it until it activates (be patient, it will take a lot of shots) and you will see a personal message from Rob Selitto, one of the level designers:
Much love to my family and friends. -Robs '98
Won Choi's Drop Pod
A Drop Pod bearing the name Wonimal has crashed in the Widow's Lair, embedding itself in the thick metal walls. The marine inside is trapped and desperately crying for help, though the player can't do anything to help him. This is a reference to artist Won Choi - one of the members of the Ground Zero team.
Always read the fine print
If you read the last line of tiny text below the credits in the quit confirmation screen, you will see that the developers thank you for reading the proverbial "small print", which most people often skip (due to its small font size). You're welcome!
A crashed drop pod in one of the areas of the Research Hangar (where you pick up the Airstrike Marker from a Gladiator) in Unit 3 has the name "Zor" written on it - a reference to Rogue Entertainment's level designer (of that time), Berenger "Zor" Fish. "Zor" is also referenced during the introductory cutscene.
Berenger "Zor" Fish (Rogue Entertainment's level designer) has left one more reference in the Research Hangar level. It's a little 3-D box with big 3D letters spelling "ZOR" in it. Using noclip command from the in-game console is the only option to see it. The box is located pretty far away from the main map (it's barely visible from your starting location). The exact coordinates are (4005 -4076 -4064) : 14. You can see your current location coordinates using viewpos command from the in-game console.
Hunter Sphere Egg
If you look carefully into the Hunter Sphere's scanner "eye", you should see the image of a loving couple.
Quake 3 Arena
Several pieces of recognizable Doom artwork appear in Quake 3 Arena. The most famous of them is probably the image of a Lost Soul on the lower side of Anarki's board. Another typical Doom image (Demonic head in a pentagram) can be seen on the back of Biker's jacket. There are also several images of the Icon of Sin appearing as wall decorations on some of the maps.
In the Deva Station map in Tier 4 is a corridor with a Shotgun in front of a teleporter. Walk in the direction opposite to the teleport and press yourself against the wall. It will open, revealing a small chamber, and a message will be displayed, tell you that you have found a secret (a nod to the original Quake and Quake 2). Inside it is something that looks like Dopefish - or rather an evil zombified version of the stupid little fish. In Quake Live, it's replaced by a chicken.
Eric Webb's Head
Among the lowest tunnels of the Demon Keep in Tier 5 is a small square room with a disembodied head resting in one corner. Its eyes turn white from time to time. This is, in fact, the head of the id Software intern (at that time) Eric Webb.
Invoking the Arena Masters
If you try to chat with the bots, most of them will respond in some way. Mentioning the name of someone from the id Software team will cause the bots to warn you not to "invoke the wrath of the Arena Masters".
Old Man Murray
The Dust Puppy
Hidden on the lower surface of the main platforms in the Bouncy Map and Apocalypse Void in Tier 6 is the image of Dust Puppy from the website www.userfriendly.org. The only way to see him is to fall off the platform and look up, or play the map as a spectator. Using the noclip cheat is another option.
Badger, Mushroom, Snake
In one of the control rooms aboard the Hannibal there is a holographic table displaying a tactical scheme of a battlefield. Three SMC squads are visible on the scheme - named Badger, Mushroom, and Snake. This is most likely a reference to Weebl's flash animation Badgers.
Red Key of Doom
Quake Live Team List
Hidden within the QZPRACTICE1 map is a list of the Quake Live team, appearing in handwriting on a wall near the bottom of a pit.