The crusty part of one's bedsheets soiled with cum from a nocturnal emission or self-handjob. Dogs prize crusty surprises as delicacies, much as we prize lemon merangue pie, and will seek them out in the morning whilst their owners are showering. Not to be confused with the crusty pillow surprise
, although there's no reason why a pillow couldn't have a crusty surprise.
Woman: Richard, come here.
Woman: It's your dog. What's he doing?
Man: Barney! What you lickin there?
Barney: really guilty look
Man: Look's like Barney found himself a Crusty Surprise.
Woman: That's disgusting.
Man: That's all right, Mr. B! That cookie's yours!