I own a "Doctor Who" T-shirt emblazoned with the caption, "You never forget your first Doctor."
It's a reference to the 11 different actors who have portrayed the Doctor over the decades and how fans of the show usually will tell you their first Doctor is their favorite.
For me, that was Tom Baker, the fourth Doctor. Although he had already moved on by the time I first saw "Doctor Who" on public television in the mid-'80s, I caught him in reruns.
At the time, the Doctor's latest traveling companion in his journeys through time and space was Sarah Jane Smith, played by Elisabeth Sladen. And maybe it's also true that you never forget your first Doctor's companion, because all of these years and companions later, Sarah Jane is still my favorite.
That made the news even more of a shock when Sladen died Monday at age 63.
Sladen reportedly had been battling cancer for a while but had kept her illness secret from all but her family and closest friends. When her name started trending Tuesday afternoon on Twitter, fans hoped it was just another silly rumor of the sort that goes around Twitter at least once a week.
Then, Doctor Who Magazine and the BBC confirmed the news.
Later, word had spread to Entertainment Weekly's website, which demonstrates just how much of a foothold a formerly obscure British sci-fi series has gained in the often provincial United States.
Sladen's death came not long after the passing of her fellow "Doctor Who" co-star Nicholas Courtney, who died in February at age 81.
Throughout the 48-year history of "Doctor Who," the Doctor's companions have played a vital role. They're our window into the Doctor's wonderful and often inexplicable world. It's hard to relate to a 900-year-old alien who flits about in amazing blue box — called a TARDIS — that's bigger on the inside than it is on the outside. But we can relate to those lucky Earthlings he deems worthy or interesting enough to invite along on his travels.
And Sarah Jane was arguably the best of the lot, which puts her ahead of some pretty tough competition, from the feisty 18th century Scottish Highlander Jamie McCrimmon in the 1960s to, coincidentally, a feisty 21st century Scot, Amy Pond, today.
Traveling first with the third Doctor (Jon Pertwee) and then Baker during 3½ seasons from 1973 to 1976, Sarah Jane was more than just someone the Doctor explained the plot to. She was smart, capable and able to take care of herself, although she did play the screaming damsel in distress on occasion — an unavoidable occupational hazard.
On screen, there was a special chemistry between Sladen and Baker. Of all the Doctor's companions, only Sarah Jane was his "best friend," and her departure from the TARDIS at the end of "The Hand of Fear" is one of the series' most powerful moments.
While most other companions leave never to return, "Doctor Who" keeps coming back to Sarah Jane. The first time, in 1981, was a pilot for a rejected spin-off series, "K9 and Company," in which Sarah Jane was the "company" to K9, a robotic dog who was another of the Doctor's former companions. Next, when "Doctor Who" returned to television in 2005 after a 16-year hiatus, so did Sarah Jane, appearing in the 2006 episode "School Reunion."
A new generation of "Doctor Who" fans was just as taken with Sarah Jane as the old one had been, and soon she was finally starring in her own spin-off, "The Sarah Jane Adventures," which has aired for four seasons. A fifth season was reportedly half filmed at the time of Sladen's death.
Before Tuesday, "Doctor Who" fans were eagerly anticipating the show's new season, which begins Saturday night at 8 on BBC America. Now, however, the occasion will be a little somber.
For a lot of Whovians, it feels like we've lost our best friend, too.