Buzz Lightyear of Star Command (2000)

S1E27 The Crawling Flesh

Zurg unleashes a corrosive gas that transforms Mira and Buzz into a grotesque, shoggoth-inspired entity. He then sends them back to Star Command, where their unintended presence leads to a catastrophic outbreak. As Mira and Buzz arrive, they unknowingly spread the strange infection, putting everyone at Star Command at risk of becoming part of the monstrous amalgamation.