What I expected to happen was...:
I thought the polar bear would return to it's normal stance when I swapped into creative mode (It was in the middle of attacking me).

What actually happened was...:
When I swapped into creative mode via "/gamemode creative" the polar bear stayed on its hind legs and continued to walk around on its hind legs instead of walking on all fours.

Steps to Reproduce:
1. I was in survival mode and the polar bear attacked me.
2. I swapped into creative mode via "/gamemode creative".
3. The polar bear stayed on its hind legs and continued to walk around like that. (It was admittedly quite funny to watch).