Storm in a Teacup

A standard sitcom plot. One or more of the characters are trying to get something apparently urgent done - they've broken someone's favorite vase, the wedding has to be just right, they're looking for that perfect gift to give to a girl. Hilarity Ensues.

Their efforts usually culminate on catastrophe, and they reveal what they were trying to do amidst tears - only to find out it wasn't such a shaggy dog after all: The vase was a gift from a hateful aunt, the wedding can be done on the backyard, one of their friends plays in the girl's favorite band. They're relieved, everyone laughs, cue the credits. The Aesop is usually "Things will be fine if you ask for other people's support".

Anime and Manga

 * In CLAMP's Wish manga, angels are running around terrified of what God thinks of their romantic entanglements. Turns out God isn't as Smitey as characterized.

Literature

 * Most decidedly not Played for Laughs in Guy de Maupassant's short story "The Necklace": A woman borrows her friend's diamond necklace for a fancy dress party, only to lose it and buy a new one, using loaned money that takes her a decade to pay back. Near the end of the story, she runs into her friend (whom she hasn't seen since the party) and reveals the truth. The friend, tears welling up in her eyes, reveals that her necklace was merely "paste" (costume jewelry), and didn't cost a fraction of the replacement's price tag.

Live Action TV

 * There was an episode of Sabrina the Teenage Witch where Salem the cat accidentally breaks a special mirror. He spends the episode meticulously putting it back together, finally succeeding and dragging it back up to the attic at the end... and someone else breaks it while he's dragging it up the stairs. And then it turns out that they had another mirror just like it and don't care about it being broken.

Western Animation

 * Every other episode of Doug.
 * This seems to happen a lot on Nickelodeon and Disney Channel.