In 2022, a proof of concept demo for a potential Gex game dating back to January 25, 2001 was dumped online. Titled "Gex Jr.", the demo features one short level in a "Media Museum" where you control Gex Jr. (presumably voiced by Dana Gould), collecting soda cans, cracking pop culture references, and using a dedicated fart button.

According to several developer quotes included with the dumped demo, it was developed by ImageBuilder Software, who were previously commissioned to make CD-ROM edutainment titles for other companies that were mostly in 2D animation, but featured some 3D rendered elements. Gex Jr. originated as a different 3D platformer demo called "DINO", starring that titular character, with all character assets being built and animated in Maya. According to one developer's recollection of the demo: "The dinosaur character was very cute. As I remember, he roared and trotted around, possibly shot his tongue out as an attack like Gex."

At some point, the team turned DINO into Gex Jr. on their own in the hopes of selling the idea, but failed. It's not remembered if Gex Jr. was supposed to be a younger version of Gex, or a son, or having any familial relation to Gex at all. However, the last developer comment seems to hint at how Gex Jr. was conceived in-game: "As far as Gex f***ing... you did play the games right? Remember the babe Agent Xtra?... I'm just sayin."