Zonko's

Zonko's Joke Shop
Zonko's Joke Shop is a store frequently patronized by Hogwarts students, most notably Fred and George Weasley.

In Harry Potter and the Prisoner of Azkaban, Harry buys several items at Zonkos on one of his illegal trips aided by the Marauder's Map. These items include a biting teacup and other such joke novelties.