A flock of sheep are grazing in a field, happily saying "baa baa" to each other and discussing life as usual when suddenly they hear, "moo moo mooooooo!"
The sheep look around to see where the cow is, but they can see only sheep. They carry on grazing as before.
"Moooooo mooooooooooo mmmoo!" they hear again.
One sheep can clearly hear the mooing next to him. He looks at his sheep-friend next to him with a worried look on his face and then asks, "George, why are you saying 'moo'? You're a sheep. Sheep say 'baa!'"
His friend proudly replies, " I know, I know. But I thought it would be a good idea to learn a different language!"
I don't understand this joke.