What do reindeer hang on their Christmas trees?

This joke plays on a pun involving the word “ornaments,” which are decorative objects commonly hung on Christmas trees, and “horns,” which are prominent features of reindeer. The term “horn-aments” is a humorous blend of these two words. The joke imagines a scenario where reindeer, instead of using traditional Christmas tree ornaments, would use decorations that relate to their own distinctive characteristics – namely, their horns. The humor arises from the absurdity and whimsy of reindeer decorating a Christmas tree, and the clever wordplay that merges a familiar holiday tradition with a characteristic feature of these festive animals.