A phrase that if yelled at a party, justifies ANY otherwise taboo action or statement that precedes it.
Can be used in any situation.
You are blackout drunk and a kid tries to get you to vomit for your own good at a party. You pull a knife out on him and everybody freaks out and then you scream RAPTOR SURPRISE. Everybody then laughs and forgets about the previous action.
Great if used as a hashtag on twitter as well.