Well, in cinema or theatre "part" would mean "papel". If so, we could safely guess that it was about some kind of "game" where the participants would assume a "part" (say, one could be a pig "oink oink", other could be a dog "bow ow", other the cat "mew meow" etc).
Let´s say the animals (people roles) would be performed along with "costumes". So in the middle of the play, they would change their props
(the heads, for example). But the switching of the parts would be simultaneous with the wearing of a foot massage slippers (to add some level of difficulty - and fun).
This was just a guess of mine, it may or may not be (like) this. So, it was just for you to get the general idea.
Notice: foot massage slippers - sandals massage slippers for foot (you can use some search machine Google, Yahoo, etc to see what it is.)