One of my favorite themes that I do is our Stuffed Animal theme. We bring our friends with us to class and introduce them during warm-ups (always have a couple extra for athletes who forget them!).
For younger kids, our friends like to watch us go upside down. I set up a specific place where our friend can sit and watch as I do cartwheels, etc.
Our friend also loves going really fast and jumping with us! He also loves to hang out upside down in a handstands and pull-overs with us (I have the kids show bear how to do it and then the kids help the bear do it)
Bear sometimes just needs some big hugs while we balance.
For older kids, I use the bear more as a prop with skills. I have them do skills where they are giving the bear a ride (giants, glides, bounders/flysprings, rolls, etc). Bears also love conditioning with athletes (leg lifts, v-ups, arch ups, tight body rolls, etc.)