The 10 best modern 'Doctor Who' episodes
Pompeii, Christmas, Fireplaces and more
5. 'School Reunion'
Doctor: David Tennant
Companions: Rose Tyler, Mickey Smith, Sarah Jane Smith, K-9
Why we Love it: Watching how the new series has dealt with the old one has always been interesting. This episode is ostensibly about evil doings at a local school and features Anthony Head of "Buffy" as our head baddie, and if it were only that it would be a serviceable episode. However, there is so much more going on – the episode is really about bringing back companion Sarah Jane Smith (Elisbaeth Sladen) and K-9 (the Doctor's mechanical dog). Sarah Jane had been a companion of both the Third and Fourth Doctors (Jon Pertwee & Tom Baker, respectively) and had appeared in a couple of specials following her departure as a regular from the series in the mid-'70s. The episode not only makes Sarah Jane and the Doctor think about how he left her, but forces both Rose and Mickey to consider their futures. Will the Doctor leave Rose the same way he left Sarah Jane? Is Mickey the technical support or just the tin dog? "School Reunion" asks what happens after the Doctor leaves, and that question is one that every companion since has had to face.