I may have related this story on the Cat before but ...

When my daughter was little we got a puppy. One day a little neighbor girl came over and they were petting the pup.

I came to attention when I heard my little girl say, "And this is his peter."

I said, "Actually, Kelly, it is his penis. 'Penis' is the real word for it."

She looked confused. She said, "But we say Peter Rabbit."

I chuckled, "Yes, you can say 'Peter Rabbit'.

She turned back to Sally, "And this is his Peter Rabbit."

Haven't found a song for it, though.