Alien Hominid makes an appearance in Castle Crashers as an unlockable character. They also appear as enemies on the Alien Ship level.
Contributed by thebigdb7
The clown princess Spoiler:at the end of the game is a reference to Tricky the Clown, an early animation made by one of the creators of the game.
Contributed by MatFarogan
On the level "Alien Ship", if the player goes left instead of right after being freed from their cell, they will see the game's producers in cryogenic stasis.
Contributed by Raiden_ Revenge