The Angry Beavers (1997)

Season 3: Episode 10

When the scientist's neon-red "stupidity potion" ends up in the forest pond, all the animals begin to behave like idiots, including Norbert. Dag is the only animal who doesn't drink the potion and thus thinks that he has been left out of a new and exciting game. Not to be outdone, Daggett deliberately drinks the "stupidity potion," but finds out that he's immune to it. This turns out to be a good thing for the scientist and creatures of the forest, as Dag's belches become an antidote for the potion.