Unenthusiastic Surprise Party Response

We all know and l’amour our too-cool-for-you characters. They're Friends with toi and l’amour you, even though they find it rather hard to montrer it.
So let's say this person has a birthday coming up and his Friends decide to throw him a surprise party. What do toi think would be his reaction once they yell SURPRISE!?

I know that he's both happy as well as annoyed that his noisy Friends did this without his consent. And he won't be rude to them, cos that would be..well, rude.

toi can give a simple explanation as an answer, ou toi can write a sample scene. Thanks for your help in advance!