Wear a jacket. Say nothing. Occasionally smile at the nearest blonde girl.
Put glitter on your face. Pout. Emotionally abuse the girl you fancy.
Walk in. Collapse.
Bring photographs of your baby/car/baby in your car. Take pictures of all the food at the party.
Don't show up.
Dress and act like a complete dick.
If you already are a dick then do the opposite of what you would usually do.
Open a cupboard. Close a cupboard. Put a bed sheet over your head. Leave.
Run around the house screaming and slamming doors.
Don't show up, but have your friend tell people that you're "there in spirit."
Go to a party you weren't invited to.
Be a bit creepy throughout the night, but ultimately do nothing of note.
Don't show up, but have your friend spend his night telling people that you'll "probably be here any second now."
Dress as you normally would, and if people ask you why you aren't in costume tell them that the Devil takes many forms.
Lie on the floor. Don't move.