SpongeBob SquarePants (1999)

S7E7 Goo Goo Gas

Plankton devises a new plan involving a gas that transforms anyone who breathes it into infants. He takes over the Krusty Krab, leaving all the patrons as babies. With the crowd incapacitated, Plankton seizes the chance to grab the secret formula. However, during a struggle, SpongeBob accidentally strikes the gas canister too hard, resulting in a massive explosion. The aftermath leaves Plankton shrunk down to a tiny baby size.