Actress Elisabeth Sladen, best known as "Doctor Who's" Sarah Jane Smith, died earlier today at the age of 63 after battling cancer.
For "Doctor Who" fans this is a major loss, as Sarah Jane is commonly thought of as the Doctor's best companion.
Sladen originally joined the show in 1973 joining Jon Pertwee and continued until 1976, creating magic with Tom Baker.
Sladen's Sarah Jane was so beloved that she returned with David Tennant's Tenth Doctor in "School Reunion" giving fans closure to the pair's relationship, while jumpstarting a new chapter. In fact she was so great she got her own spinoff, "The Sarah Jane Adventures."
Both Tennant and Matt Smith, the Eleventh Doctor, made appearances on "Sarah Jane," making her one of the few people to work with multiple Doctors.
At the time of her death, the fifth season of "Sarah Jane" was filming, so it's not yet known what will happen to the show, but hopefully she will be honored appropriately in the upcoming sixth season of "Doctor Who."
Her loss leaves a huge hole in the entire "Doctor Who" universe.