Brad Pitt’s big “acting” breakthrough (e.g. not just being in a movie to look pretty) came in Terry Gilliam’s “Twelve Monkeys” which starred Bruce Willis.
Willis plays a time traveler who has been sent back in time to prevent a plague with the only clue being the sign of the “Twelve Monkeys” in the film’s title. However, when he arrives he is thought to be insane, so they put him in an institution where he meets this guy:
Pitt’s character is delightfully unhinged, most likely going through a manic episode with non-stop talking, mostly about how badly humans treat animals. That’s not the creepy part.
Willis and Pitt meet again, but this time we find out that Pitt’s character is a rich trust fund kid who is committed to animal rights. At all costs. He’s building up a group of paid militants to do things like raid research labs and break into zoos with zero though as to the consequences of doing so. Although you can’t really question his cause, it’s clear throughout that although he’s somewhat more controlled outside the asylum (where his daddy had him locked up) he’s still being driven by the delusions of grandeur that brought him to the asylum in the first place. The name of his organization is, of course, “The Army of the Twelve Monkeys”.