And who doesn't root for the underdog? Especially at the Westminster dog show. ABC's David Wright takes us right into the doghouse. Reporter: They are canine supermodels. Primped and poised. Some... See More
And who doesn't root for the underdog? Especially at the Westminster dog show. ABC's David Wright takes us right into the doghouse. Reporter: They are canine supermodels. Primped and poised. Some looking part dog, and also part brush you might find at a car wash. But they are purebreds, one and all. Until now. For the first time ever, the nation's oldest and most elite dog show is allowing dogs like jimmy here to compete. He's a mixed breed. No pedigree. In fact, he's a rescue dog. And what's his story? He was dumped at a shelter in Wiley, Texas, at about 7 weeks of age because he had ringworm. Reporter: But jimmy now has his shot in the ring at the Westminster dog show. Think of it this way -- the world's most exclusive club is opening its doors to the average Joe. The mutt could be a champion. Unlike some other competitors, jimmy has never had a good hair day. If I brushed him, his hair would be kind of wavy and he would just shake himself and he would look like this again. Reporter: But jimmy has other talents. Jumping through hoops. Racing through tunnels. Up over that thing. And through all of those things. He's 1 of 16 mixed breed dogs hoping to beat the purebreds in the agility. What would it mean? Any dog can do it. And just because your dog doesn't have a pedigree doesn't mean it's not an athlete. Reporter: They always said, every dog has his day. Now, even the underdog. This is a huge test, buddy. This is a huge test. Reporter: David Wright, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.