Kinda like Twister.
One, maybe three people get in the middle. Everyone else is in pairs (maybe triplets). The middle person/people say something like "elbow to knee." The other players, in their pairs or triplets, all put their elbows on each other's knees. Or vice versa. So, if there are two players, player A has his elbow on player B's knee, and player B has her elbow on player A's.
On and on it goes: foot to shoulder, ear to belly, nose to toe, until players are significantly contorted. At which time the center person/people say "People to people" and everyone must find a new partner or two.
Often, people just want to be IT and hang around until everyone else is partnered up. Be cool with it.
Todd Strong told me of another variation, called "Common Ground" Instead of body parts, name anything that you think people might have in common: "the same kind of shoes" "the same color hair" "born in the same State"... Everybody races to find partners with that commonality. And a new round, with hopefully a new IT, commences in like manner.
See also this.