All participants much choose an animal. They tell everyone what their animal is, then demonstrate "being" that animal (involves moving like one, and sounding like one) Once all is done, Madrich/a says "start", and everyone begins pretending to be their animal (everyone must have a different animal). At a random point, Madrich/a can shout "trees", upon which everyone must pretend to be a tree. Then, Madrich/a shouts "animals" and chanichim resume being animals. HOWEVER. When the chanichim switch from "trees" to "animals" they must choose an animal that is not their own, but rather someone elses. If two people choose the same animal, they are both out. So, basically, you have to (in a short space of time) remember the animals chosen by the others AND try to guess which one nobody else will choose.