Ruined scenes with animals.

Yestereday's entry got me thinking. What other shows/episodes had horrible or great animal actors or roles?

I always remember in the Black Stallion the beach scene. The horse is supposed to be sans tack. But the shadow, that they artisitcally keep flipping too, shows a horse with its mouth wide open. Something that ONLY happens when there is a bit in the mouth and the horse is trying to evade the bit.

I have asked these questions on my favorite forum (chazhound.com if you don't know) and will hopefully have a more full post later with other opinions.