How about these lesser-known sumo wrestlers themselves? BTW, the following characters all come from the Netflix series, "Go, Dog. Go!".
Tag Barker: Tag Barker has always wanted to be a sumo wrestler herself but her family, including her brothers, their parents, including their father Paw Barker, and their neighbors had always reminded her that sumo wrestling's always been a male dog's sport. Little did her brothers, parents, and neighbors know that Tag is determined to prove to them that a female can be a sumo wrestler, too, as she joins the Multiversal Animal Sumo League and becomes another one of the female sumo wrestlers (or the first, depending on when she arrives). In addition, she is also going on a quest to prove she's the biggest, strongest, and fattest female sumo wrestler in the world. She may have learned the basics of sumo wrestling (or maybe she hasn't, yet), but she's just getting started.
Scooch Pooch: As Tag Barker's neighbor, he's always a bit shy about joining the sumo league, as he felt like he could get hurt. However, his mom, Sgt. Charlene Pooch, would like her dear sweet little boy to at least try and compete in the sport of sumo wrestling itself. Eventually, he agreed to sign up for the Multiversal Animal Sumo League and make not only his mom proud, but also his neighbors and fellow citizens themselves, too. This young puppy is about to become big and fat like a sumo wrestler, and if he wants to become a famous sumo, then he's gonna have to Go, Dog, Go the Distance and retire a sumo champion or retire trying.
Frank: He's a schemer in Pawston, and everybody knows it. So, when he heard of a sumo league accepting animals from many different universes, he signs up and launches his scheme to win a sumo tournament by any means necessary, even by cheating. Hopefully, he'll win by cheating without anyone finding out about his ruse, right?
Yip Barker: As the littlest one of the Barker family, her parents, brothers, sisters, and neighbors thought he would make a good sumo wrestler, so they decide to sign him up for the Multiversal Animal Sumo League. There, he will be competing against other big fat baby sumo wrestlers and train alongside them too.