"So no point being a bat if you can't flap around in caves, fly around folks' heads and generally cause a nuisance.
Hmmm...but there's some else missing. Yeah, how am I going scare people if I can't make a scary noise? I need to find something that makes a noise I like and make a noise like that.
Ahhh...I remember the old days when evil master Vosperlich used to play ball with me through the caves. He would throw the ball as far as he could down through the caves and I would chase after it as fast as my little green wings could flap. Oh happy days! Other bats would say he was just trying to get rid of me for a bit so he could carry on with his evil experiments, but they were just jealous he wanted to play with me.
Oh, how I remember the ball's squeaks would echo through the cave as it bounced off the walls. I loved that squeaky ball. That's it! That's the sound I shall make, how wonderful! I shall squeak as loud as I can and maybe one day my master will hear the squeaks and come back and play!"