Brooks doesn't really have the acting range to be able to spaz out convincingly. That's the core issue. He's really good at acting when he's just playing 'normal', but it doesn't translate when he's called to do more than that. He also gives some similarly bad-acting in "Our Man Bashir", and when he screams "I WILLLLL!!!!" in WYLB, and some other episodes that I don't recall off the top of my head at the moment.