A Guide to Classic Who references in New Who episodes. Meet the Friends of Doctor Who...
Sarah Jane Smith was an investigative journalist and companion to the Third and Fourth Doctor, and star of her own failed spin-off "K-9 & Company."
Sarah Jane Smith joined the Third Doctor in the first story of Season 11 ("The Time Warrior") and worked with him until he regenerated into the Fourth Doctor.
She stayed with the Fourth Doctor until early Season 14 ("The Hand of Fear").
Five years later. Sarah Jane received an mysterious crate for Christmas. In the crate was a third K-9 unit, and it lean to the pair having a series of one adventures (the failed pilot K-9 & Company).
Two years later, she was stolen and forced to join the four Doctors and their companions in "The Five Doctors."
Since then, Sarah Jane Smith appeared, obviously in The Sarah Jane Adventures, as well as appearances in the new Doctor Who.
This article refers only to references within the classic series, not the new series.