A cat named Dog and a dog named Steed.

I once had a cat
I called him Dog.
I bought him a collar, and
A tag that spelt out D-o-g.
I'd chase him down perches
And find him chasing bees
But never picking my paper
Or wagging to please.
I didn't like cats
But he was my Dog.
So I watched him,
Pick after his poop
Lick his coat clean
Get his milk,
And leave no trails.
I loved him much,
This Dog of mine.

I now have a dog
I call him Steed.
And I love him much,
This Steed of mine.