True story. My grandmother had a collie mix out on her farm. Some gentleman gave her a very young sheep with a lame rear leg. Following the collie around it grew up thinking it was a dog. It herded the cows when they got out. It chased cars. It even bleated out what was supposed to be a bark.
One of the more bizzare things I ever saw was two wild dogs come prancing up to it thinking they were in for an easy meal, turn and run for their lives when the sheep turned and charged them.