Hilarious Antics are a type of ability that John Egbert has in Homestuck. It's not completely certain what qualifies as Pesterchum Hilarious Antics or if it is just plain stupidity, but the fact is that John is capable of accomplishing these feats. Hilarious Antics are part of John's mode of humor, and he readily refers to irony and props to accomplish them. Often cake is the subject of his Antics,and as there is copious amounts of it lying around the house, it's not very hard to see why John would make use of it in his jokes. However, despite his penchant for humor, John gets lambasted by his Dad in prankstering, losing a few precious points in his Prankster Gambit, and his fellow Chums on Pesterchum berate him endlessly because of his interests. Seems like his antics aren't that hilarious after all.
Whistles has also engaged in Hilarious Antics.