There is a secret portal located towards the upper-left corner of the level "The Project". Going in it will take Gex to a hidden room with a unique enemy blocking an exit to the level; a random man walking towards Gex. Hitting the man will cause him to vomit, and his kill animation shows large amounts of blood shooting out of his neck before dying. It's unknown who this person is, though it could be a self-insert by one of the game's developers.
Contributed by MehDeletingLater