Bug in minecraft's newest snapshot

I recently started a new survival world for all new snapshots. I was terrified when I saw my cat without one leg. It isn't that much a problem but it is surely a weird one.

Ps. 

I just wanted to ask out of curiosity because I typed my alt.  nickname on this site and just wanted to know if it will be changeable after a short period of time. 

Thanks for your help!

Kyle