Yeah, it was a cartoon. Rankin and Bass perhaps.
It takes place the night of the Nativity and about how all the animals were able to talk for that one night.
The only thing that I really remember about it was near the end when the animals wanted to use their new found talents to spread the word of the Christ child but, as the star faded so did their ability to talk. I thought it was sad.
All in all though, it's probably best that animals don't talk. I hear all they want are Cheeseburgers.