not bad.
I think you kinda rushed things a bit. It just all kinda happened at once. Build the story a bit before you just jump into the main event.
Also, you do kinda need sound effects. All things considered, this was more of a music video than anything. It wasn't all that bad though. I do like where it's gonna go. Also, voice acting wouldn't be a bad idea either. Even a yoshi sound might be better than nothing.
Anyway, I hope this will help you in future flashes. I am a bit nitpicky towards sprite movies because I like to try and help improve it as much as I can.