If a super villain's powers were going to be released by something beyond their control or knowledge (sort of like if Bruce Banner somehow didn't know anger turned him into The Hulk), what's a good thing to set the super villain off?

When he falls asleep the powers take over, Fight Club style.

Or he could experience periodic blackouts and bouts of amnesia which are a result of his memory blocking out the usage of his powers.

Or you could make him have anterograde amnesia, which doesn’t allow him to form new memories past a certain point (that would make the character a little hard to deal with though)

You could also do something like Hulking out but he just has no memory of it when he wakes up.

Inability to hold an erection.

Hiccups! involuntary bowl movements or maybe he could be hypnotized and respond to the world lollipop (yeah that’s right its a scrubs reference, what are you going to do about it).

Hmm maybe that wasn’t as helpful as I thought it would be. What about: a parasite, some form of epilepsy, an emotion, an observer who is controlling him, allergies. It’s probably a good thing I’m not a writer.

Secondhand smoke. Strong EM radiation (think power lines).

Proximity to some random person. That, I think, could be a winner. Sort of like the two part epoxies—when they get close enough together perhaps something happens to them both.

Sexual arousal. Being sexually frustrated will only add to his evil.

Pain of any kind or magnitude. Tooth ache, if he stumps his toe, dog bite, sun burn…He can’t control any sources of pain.

I think it should be a pair of supervillains who are enraged by a person’s poor fashion sense and immediately try to humiliate their trigger in front of millions, Oh wait, that is already a TV show. . . never mind.

@markyy bowl movements as in he is a professional bowler, or did you mean bowel movements? A professional bowler with involuntary bowel movements could make for an interesting game. =)

I think jealousy could work quite well for your needs.

@evelyns_pet_zebra sorry, I was talking about ‘bowel’ movements. As for the bowler I would not want to clean up after him. I think @andrew gave a good reason. Being close to some person (maybe in combination with some emotion like love, jealousy or hatred) would be a killer reason. Hatred might be too obvious, but to never be able to be close to his lover would be such a sad story I would develop empathy for the bad guy :)