David Smart (in-universe)

David Smart was a junior ringmaster in a circus, where his sister, Gabriella, had a performing dog act. (TV: )

Biography
While David was waiting for Gabriella to do her act, the Third Doctor showed up in the Whomobile with her and one of her dogs, having been helping her look for them when she lost the dogs. Gabriella then went off again with the Doctor to find the rest of her dogs. (TV: )

Behind the scenes

 * David Smart portrayed himself in Billy Smart's Children's Circus.