Reference

Several notable "Doctor Who" spin-off series have been produced over the years, expanding the universe of the beloved sci-fi show. Some of the most well-known spin-offs include:

1. Torchwood: Created by Russell T. Davies, this series follows the Torchwood Institute, a secret organization that deals with extraterrestrial threats. It originally aired from 2006 to 2011 and features Captain Jack Harkness, a popular character from "Doctor Who."

   

2. The Sarah Jane Adventures: Another spin-off created by Russell T. Davies, this show focuses on Sarah Jane Smith, a former companion of the Doctor. It was aimed at a younger audience and aired from 2007 to 2011.

   

3. K-9: This series, which ran from 2009 to 2010, features K-9, the Doctor's robotic dog. The show is set in a futuristic London and follows K-9's adventures with a group of teenagers.

   

4. Class: Created by Patrick Ness, this spin-off is set at Coal Hill Academy, a school that has been a recurring location in "Doctor Who." The show aired in 2016 and focuses on a group of students and their encounters with alien threats.

   

5. Big Finish Audio Dramas: Numerous audio dramas have been produced by Big Finish Productions, featuring characters and settings from the "Doctor Who" universe. These include "Dalek Empire," "Gallifrey," and series centered on various Doctors and companions.

For a more detailed look at these and other spin-offs, you can refer to Wikipedia and other comprehensive fan resources.