Jim put Dwight’s stapler in Jell-O on The Office.
The prank appears in “Pilot,” the first episode of the American version of the sitcom. Dwight Schrute arrives at work and discovers that his stapler has been encased in a mold of yellow gelatin. Jim Halpert watches the reaction with characteristic amusement, establishing their comic rivalry almost immediately.
The joke is more than a random office gag: it introduces the central contrast between Jim’s playful, improvisational personality and Dwight’s rigid, rule-bound intensity. Dwight treats workplace routines and possessions seriously, so the harmless prank becomes disproportionately irritating to him.
The American scene was adapted from the British version of The Office, where Tim Canterbury puts Gareth Keenan’s stapler in jelly. The U.S. pilot transferred the joke almost directly, changing the characters and using Jell-O, the American brand name for gelatin dessert.
A nearby detail fans often remember is that Jim later puts Michael Scott’s “World’s Best Boss” mug into Jell-O as another prank.