The Ridley we saw IS playable due to the "unfinished" animations. I use quotes because the animations are in fact finished and it only looks "unfinished" because that's how all of the playable characters move. Due to the speed of the game, with people being able to pull off a multitude of moves in mere seconds, theres no room for smooth animation transitions. This makes it look "jerky," and specifically due to his tail's length, it would probably warp around.Ridley's shadow acts weird because the animations obviously aren't finished. His whole body stops completely at a certain point in the video with the exceptions of his wings, with his arms being stretched forward in a very weird manner. This is a very obvious sign of him being a work in progress, and being educated in 3D animation myself it was something I noticed the second I saw the shadow too. The wings are animated seperately from the main body, which is also common for winged creatures, Skyrim does it with its Dragons too iirc, and this is not something they'd do with a character as it'd lead to weird bugs and less control over the model, but it works much better for a scripted AI. It would also explain why he hasn't been shown since him being teased back in August, and also explains why he still wasn't shown full body despite being confirmed as a stage hazard.
You guys know how much I want Ridley, but it's a bit tiring to see the argument that his shadow acted weird when there's an explanation for it. Judging from the little we saw of him he'll also be more random than his Brawl counterpart, instead of flying idly in one spot and waiting to bust out an attack he'll likely fly around constantly, which is where splitting his model up in sections makes sense (in this case it seems to simply be split between the wings and the body.) The latter part is just speculation though.
The Ridley we saw isn't playable, that's one thing that's for certain.
Like i said earlier, anyone with experience in 3D modeling can see all of these things.