Unenthusiastic Surprise Party Response

We all know and Liebe our too-cool-for-you characters. They're Friends with Du and Liebe you, even though they find it rather hard to Zeigen it.
So let's say this person has a birthday coming up and his Friends decide to throw him a surprise party. What do Du 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.

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