Once I swallowed a horse to catch a cow. I swallowed a cow to catch the goat. I swallowed a goat to catch the dog. I swallowed a dog to catch the cat. I swallowed the cat to catch the bird. I swallowed the bird to catch the spider. I swallowed the spider to catch the fly.

I don't know why I swallowed the fly.

(you guys are more predictable than I expected)