>>285232535
>>285232930
The flopping ears might not be dynamic bones, either. 

Your VR controllers detect hand gestures and send those to vrchat. When creating an avatar, you can assign animations to these gestures. By default they're just like "animation thumbs up" and "animation open palm" etc for animating the avatar's finger bones, but most avatar creator replace these with custom ones that also animate the avatar's eyes and faces for expressions.

Occasionally people extend these to animate other bones on the avatar like tails or ears for extra effect, so you could have an avatar that also wags its tail or moves the ears when you give thumbs up or any other gesture. That might have been what you were seeing.