After being rejected sexual release from your parter, you wait for them to fall asleep, elavate to your haunches and stroke your donger until you are ready to ejaculate.... at that moment you slap them in the forehead and yell "surprise" as you paint your load across their unsuspecting face.
When you think you took a quick, little shit and then look down in the toilet bowl afterwards and it's the biggest log of shit you've ever seen, Surprise!
I was at a party at my friend's house and really had to go, little did I know I was in for The Surprise Party that clogged the bowl.
doing anything that makes someone upset or angry. "you ruined my surprise party!!! now i can't trust you anymore"
describing when someone becomes irrationally angry. "gosh, what did you do ruin her surprise party?"
to look on the lighter side of a bad situation. "at least he didn't ruin your surprise party"