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
Lead Designer Justin Knorr, frustrated with all the cuts being made to get the game to ship, put a series of hidden messages for players to find. The first messages told the player how to access a secret level select screen, and encouraged them to pick a specific level, in which he placed more messages berating the company for cutting so much content. He included the head of product development's phone number, and suggested players call it and complain. The playtesters found these messages, and Justin was fired.
Contributed by RadSpyro
Originally, the game was about a stunt man named Gecko X, who worked for a studio that was in financial trouble due to the main antagonist, Karl Chameleon. Each level would be themed around a Hollywood action movie genre, which would show stock footage of old Hollywood movies at the beginning and allow Gex to run around and do "stunts". The better the player did in the level, the more money the "Movie" made and therefore the better the studio did.

The idea was dropped because the developers found it hard to base a game around a real world theme while still making it believable and fun, compared to Mario and Sonic, which were based in fantasy settings and therefore nothing that appears in the game needed to be explained. The change in plot and setting to 'TV Land' allowed the developers to have this fantasy setting and some freedom to do whatever they wanted.
Contributed by gamemaster1991