Berserk Button/Theater

When a nice, normal character suddenly goes into a rage, you've hit his Berserk Button.

"Kate: What are you trying to say? That all Monsters look the same to you?! Huh? HUH? HUH?!"
 * Dogberry in Much Ado About Nothing goes berserk upon being called an ass. And then he tells everyone not to forget it.
 * This was partly an Actor Allusion. The same man (William Kemp) also played Nick Bottom in A Midsummer Nights Dream. Three guesses what he turned into in that play.
 * In Twelfth Night, Orsino very nearly loses it when he hears that his lady-love Olivia has married his page, Cesario. However, careful listening to his monologue reveals that what he's really mad about is losing his page.
 * Cyrano's nose in Cyrano De Bergerac: In Act II, his fellow cadets claim that even using the word "nose" is sufficient to send him into a murderous rage. The worst it does onstage, however, is trigger a stream of Unstoppable Scathing Sarcasm where he comes up with an impromptu list of 20 better jokes than "Big Nose." Cyrano was also about to throttle Christian for testing just how far he could push him with a hurricane of nose puns and only stopped when he realized who he was. It's present in the R Emake movie Roxanne, as well.
 * Chicklet from Psycho Beach Party takes on her evil personality at the mention of the word "red."
 * The vaudeville sketch Slowly I Turned is based on this, and has been homaged in various songs and films.
 * And an episode of I Love Lucy.
 * Jonathan Brewster in Arsenic and Old Lace will try to strangle anyone who says that he looks like Boris Karloff.
 * Nathan in Sweet Gay Baby Jesus seems much more calm and level-headed than his boyfriend, Jed- until said boyfriend's actually threatened, and then he.
 * Avenue Q: Kate Monster. One word: Racism.

"Fiyero: Boy, you think I'm really stupid, don't you?!
 * Seems to be a sore spot for Gary Coleman too, although he gets even angrier if reminded of what his parents did to him.
 * Wicked: Galinda is terrified and upset when she doesn't get her way.
 * Despite the fact that his Character Song flat-out states that he's stupid, Fiyero becomes furious with Elphaba when she treats him like he is after they rescue the lion cub:

Elphaba: [surprised] Well, not really."


 * Into the second act, Elphaba becomes his Berserk Button, even lashing out at Galinda for appearing so unconcerned about her best friend's disappearance, status as enemy of the state, and the vast amount of rumours about her - like the one where pure water will melt her...
 * Fiyero is Elphaba's Berserk Button, so much so that half of the song "No Good Deed" is spent with her screaming his name in agony and desperation, as he is . "No Good Deed" is also her Heroic Blue Screen of Death, Sanity Slippage Song, and Villain Song.
 * Mistreatment of people and Animals also sets her off, which is what causes - well, at least half of the problems in the play. She even starts a fight with Glinda for talking about Fiyero as if he were her property.
 * In The Effect of Gamma Rays on Man-in-the-Moon Marigolds (now that's a Long Title), Ruth mentions her mother's high-school nickname, Betty the Loon. It doesn't end well for Ruth or for her pet rabbit.