Help! Any advices?

Went through this a couple of times today. I still have no idea

Start screaming like you saw a spider and then cry when they stop singing then smack your face into your cake and laugh.

Sit there and be awkward.

Choppily swing along to the tune accompanied by a barely audible out of rythm clap and make eye contact with every single person (obviously not at the same time. Hold eye contact for 5 seconds, then move to the next). To smile or not is up to you.
That'll teach them to make things awkward for you!

http://lmgtfy.com/?q=What+to+do+when+people+are+singing+happy+birthday+to+you

You’re supposed to do a slow striptease in culminating in you arriving in your birthday suit by the end of the song

I sit there and bask in the glory of having people sing to me

smile and laugh

SING WITH THEM and replace "you" with "me" in the lyrics.

Smile awkwardly