What is a good subtle Background game you can play at a party ?

Throwing a party tomorrow and I would love to have kind of a passive/subtle game going on in the background. Sth simple and where you do not need to prepare to much.

First idea was sth which I played on a two day lasting workshop. It was sth called “vampire”. Everyone draws a piece of paper, some people are vampires others are not. Vampires can “bite” when they are alone with one single person, or more vampires are with one single person. This person then turns into a vampire him/herself and can act as such.

Unfortunately the location where the party takes place and has not that many rooms, so people might flash accidentally who the vampire is when they are bitten. But sth in that direction would be fun