Notes:

Dopefish can be found in the game Rage, from Id Software.

This Easter egg is located at the Mutant Bash last arena. The player has to shoot three lights and then a dopefish pops up; shoot that three time as it appears from behind the painted waves to gain bonus money. See video here, and note that this also makes earning the "Bringin' Home the Bacon" Achievement/Trophy much easier.