SpongeBob SquarePants - Season 3 Episode 36 -

SpongeBob and Patrick buy a prank called Invisible Spray. After taunting each other with the spray, they run out and decide to haunt Bikini Bottom while being invisible, preferably being ghosts. But with their last victim Mr. Krab, he washes them out with water and exposes them nude (they took their clothes off because the spray stains clothes) to the whole Krusty Krab, embarrassing them.