I laughed until I became a horse

1st girl: My horse is a pony

2nd girl: My horse is a princess

3rd girl: My horse is a unicorn

4th girl (whose horse is the Horse of Darkness and can turn into any horse except Shadowfax): MY horse is a Unicorn Princess!

(The Horse of Darkness is annoyed. The Horse of Darkness does not like being a Unicorn Princess!)