Ringo was a single prisoner among the hundreds kept in captivity in the Colosseum whom the Tenth Doctor met when he was arrested for "borrowing" a horse. Ringo's true name was never actually known, it was just a nickname the Doctor thought up when he named the only four prisoners who would talk to him. The Doctor thought Ringo was skinny.
Ringo concluded that the Doctor must be foreign or "completely barmy", and the others agreed he must be foreign. Besides that, he never really said much. He was jailed for selling fraudulent Greek art despite worshipping Roman gods.