Well, it IS about a pet...kinda

Once upon a time, there was a poem. A magnificent and solemn poem, about a boy and his pet. It goes like this.
I made myself a snowball, as perfect as could be.
I thought I'd keep it as a pet, and let it sleep with me.
I made it some pajamas and a pillow for its head.
Then, last night, it ran away--
But first, it wet the bed.