Warp Darkmatter attacks the planet of Binipinardia with the Crater of Banpanaliya, a powerful weapon that holds a secret: it contains a secret gas that devolves everyone who smells it. As a result, the Binipinardians get devolved into lemur-like creatures. Team Lightyear also becomes infected: Buzz gets devolved into a caveman, Mira becomes blue sludge and Booster becomes a dinosaur-like creature, leaving only XR to fight Warp and Zurg's Hornets.