The Impractical Joker

S2, E21: The Joker pulls off a string of key-related pranks throughout Gotham City, then with his magic box, proceeds to snatch a priceless jeweled key right under the noses of Batman and Robin. The Dynamic Duo wise up to his ways and thwart him at their next encounter. However, the Joker has more devious plans to do away with them both before his final caper.