Thunderpants!
Explanation: This joke uses a pun to create humor by combining “thunder” with “pants.” The word “thunderpants” sounds like a playful term for underwear while evoking the image of clouds, which are associated with thunderstorms. The humor arises from the absurdity of clouds wearing clothing, particularly “thunderpants,” suggesting that they have a whimsical, human-like quality. The joke relies on the playful language and the unexpected association between clouds and a type of clothing.