Now, I'm not the best scripter out there yet, but here's my two cents.
You'll need either animation sets for each general pose of the game, or to be comfortable with forcing contortion of characters in script. Either way, each Circle will need code that tells your character to change their animation, or attatch their body part to it. Each Circle will need an if statement that refuses to let a character attatch to it IF someone else is already on that square.
You'll need a Random Number Generator, actually two of them in one machine. One for body parts, and one for colors. Store as currentBody, and currentColor, place results into those variables every time. An exception for forced play would need tossed in if the same number comes up twice in a row, or if that rule is currently in effect. It could be touch based, or timed, depending on your preference.
That said, storage variables for each body part that dictate what happen would also be used, and swapped out by spin results that match the body part. The Spinner/Number-Generator would also need to send a message on a silent channel, like 123 or something, with each Circle having a Listen state, to share the info of the turn. You can't change your leg to blue if red was spun! That's how such rules would be implimented.
Ultimately, the issue is that since characters are used, not true bodies, nobody will "fall". Another RNG could exist, to make you randomly fall, but that's kinda uncool since Twister is a flexibility/skill game. I suppose you could assign values to each tile used, in a way that you could choose which player positionings are the highest risk poses, and use them as variables to modify the RNG, making it easier to roll a falling number the harder the pose.
Seeing as I suck with animations and body moding, and am average at best with scripting, this is all I have. A fall animation, position animations, a few rngs, a difficulty formula based on what should be contortion, and people who are willing to not cheat or grief is what you'll need, plus a good scripter and potentially a good animator, pending.
Oh! Almost forgot, you'd probably need a worn item of some sort, to initialize players. And of course, the player will have to authorize the item to animate/deanimate them, which is where cheating becomes a factor. If they refuse the fall animation, they're annoying. Odds are, they'd be asked each turn if they wanted to allow the object to act on them, which could lessen the fun. But hell, I've tried to puzzle it out in English, hopefully give some people a bit of inspiration or a head start, yeah? Or a basis on which to figure how much they want to charge for it.