Dopefish

The Dopefish is originally an enemy from Commander Keen IV, designed by Tom Hall, a large green fish, prominently bucktoothed, and famous as the second stupidest creature in the universe (the first stupidest being the Ravenous Bugblatter Beast of Traal from Douglas Adams' The Hitchhiker's Guide to the Galaxy book series). Its thought patterns were described simply as "swim, swim, hungry, swim, swim, hungry".

Easter eggs referencing the character were common in Apogee Software games, and have since become an industry wide in-joke. The dopefish itself, or the sentence "dopefish lives!" have appeared in Quake, Quake II, Rage, Daikatana, Anachronox, Duke Nukem 3D, Descent, Kingpin, Max Payne, Deus Ex: Human Revolution, and more.

Doom (2016)

 * Take-out boxes of "Dopechan Noodles" can be found in various areas of the Mars base.
 * The "Intimacy is Best" Rune bears a strong resemblance to the Dopefish.

Doom Eternal

 * The chainsaw is identified as a "Mixom Bucktooth Dopesaw".
 * One of the books in the Fortress of Doom is entitled "From Nopefish to Dopefish: A Dope Tale".
 * Three giant dopefish can be found in the Cultist Base. The first is hanging from a rope, the second is stuck in a cracked ice wall, and the third is placed on an altar in a little evil shrine.
 * Many brands of candies and snacks use the dopefish as their mascot, including "Fruitchoos", "Dope-Chan", "Okasushi!", and "Dopenuts!".

Community mods

 * Depicted on a wall in E3M7 of Doom the Way id Did.
 * The dopefish appears as a boss monster in MAP32 of Doom 2 the Way id Did.
 * Found on a wall in Z1M4 of Knee-Deep in ZDoom.
 * Referenced in E3M2 of ZPack.
 * The "Dopefish lives!" message is seen on a graffiti in MAP12 of Hellcore 2.0.