10 Doctor Who Moments You're Missing From Expanded Media
4. Sarah Jane And K-9
Sarah Jane Smith is probably the most iconic of the Doctor's classic companions. But when she returns in both the Five Doctors and School Reunion, she is accompanied by a K-9 unit. How? K-9 is first introduced to Doctor Who in the Invisible Enemy, in 1977, but Sarah Jane left the TARDIS a year prior and was not accompanied by the iconic robot dog, so how come he is present in her later appearances?
Enter the first Doctor Who spin-off: K-9 and Company. In 1981, the one of special a Girl's Best Friend aired, and was an unsuccessful pilot which would have kick started this new series. The special sees Sarah Jane receive a special package from the Doctor, containing the new K-9 Mark III, and the pair of them stop a cult. The gift from the Doctor truly showed he meant what he said to Sarah in that he would never forget her and, as far as we've been shown, she is the companion revisited by the titular Time Lord the most.
Whilst this spin-off may have been unsuccessful, it partially sets the groundwork for Sarah Jane's later returns, and her modern spin-off, with her version of K-9. It is therefore because of this failed spin-off that the pair remain a much loved pair in the New Who era.