Gex is from a time when cool animal mascots were all the rage.
Gex is a side scrolling platformer where you play a gecko (before Geico popularized geckos). You can climb on walls, hit enemies with your tail, and use your tongue to pick things up. The idea of the game is that you are sucked into a TV and need to fight through a whole bunch of worlds based on rip-offs of classic TV shows and movies. Gex likes to make wisecracks and either he or the narrator likes to imitate characters like Shaggy from Scooby Doo. It is entertaining at first but gets annoying after a while, especially if you keep dying and hearing the same things over and over again.
This game originally was released for the 3DO, and I originally played it for the Playstation, but it was released in a large box for the PC by Microsoft of all companies. The game was successful enough to spawn multiple sequels.