(By which I mean a non-human animal.)
My earliest memory full-stop is crawling behind my parents' couch after the white cat they had when I was born. In fact, my first word was "cat."
I also have very early memories of feeding and petting our neighbors' horse, Todie. I remember one time he bit my finger (accidentally, of course), and I tried so hard not to cry, because I was afraid if my mom knew he'd hurt me, I wouldn't be able to see him anymore.
Yes, that's my wee diaper-sagged ass feeding carrots to Todie. I was about thirteen months old in that photo, which was taken the summer of 1975. Mama Shakes and I used to walk down to the pasture, which was maybe 100 yards from our house, and it always seemed like the longest walk in the world, because I couldn't wait to see Todie, and his small companion pony Princess.