The original poster Philip_Lombardo is right to call that scene out as ridiculous. A huge crowd of people singing with a band in a room and one guy peeks around a door and starts singing with them and everybody stops like someone set off a bomb. This is one of 100 ways in which GF3 is sloppy.

If taken literally, The Ant would probably be advertising to the room that he is homosexual and is looking for companionship that night.