The series featured many connections to "Doctor Who". The Slitheen family, who first appeared in the "Doctor Who" episode "Aliens of London" appeared in two stories in the first series, and the Sontarans, who first appeared in the "Doctor Who" story "The Time Warrior" featured in two stories in the Second series. The character Doctor Who also appeared in the episodes "The Wedding of Sarah Jane Smith" (played by David Tennant) and "Death of the Doctor" (played by Matt Smith).