Beasley Gloom
From Blaseball Wiki
Beasley Gloom is a pitcher for the Charleston Shoe Thieves. He is a dog. He's just the most adorable dog you've ever seen play baseball! Look at his wittle paws and shoes! We All Love Beasley!
It is worth noting that as of time of writing, there is nothing in the rule book that says a dog can't play blaseball.