Here is the email exchange with Lisa that describes it best:
Sarah: I'm so happy you are coming on Friday! Even though we are most likely going to be laying in small sad puddles of exhaustion on stage. Except for my left arm, of course.So I think Jill is right. I didn't dance this way before my transplant so this can only be the doing of Thumper. I suspect my Thumper used to be a dancer. I'm actually 99% sure that he was, but since I don't know, I'm not going to say for sure. I've done my research but have never heard from my donor family. If I did, the first thing I would ask is if Thumper was a musically inclined - either dancing or singing. And if he liked video games.
Lisa: I can just see the choir, all laying in a huge heaping pile of exhausted
sweaty bodies with you hopefully on top and then wait...one sees movement! And its your arm, starting to flop around like a newly caught fish. But to a beat.
This is the first time in a long time I've felt the spirit of Thumper. He was strong when I first was transplanted but then everything was loud, confusing and overstimulated. I sensed he was a bit wary - comfortable, but still finding himself in this new person doing new things. But I'm hearing him now - loudly. He loves to dance - he wants to dance with me. And I'm happy to oblige. So if you see me on stage and see that left arm whacking out - you know that it's not me dancing wrong, that's my Thumper saying hi.