I got stuck on the grass block and couldn't move

Summary

I was on speed 100 and i got stuck on a grass block and couldnt move. I couldnt even brake blocks. I was on creative, and when i did /gamemode 0, it said i suffocated in a wall. When i respawned i spawned in a blue vortex thing and when i looked at my skin it was a messed up steve.

Steps to Reproduce:
1. go to minecraft snapshot 14w19a and create a new world
2. do /speed (your name) 1 1000000 100
3. Try to get on a grass block and then get stuck