Trying to explain the British sci-fi TV show "Doctor Who" to people who've never seen it before can be a bit challenging. I know I've been met with a few raised eyebrows when I tell people about the concept: it's a show about an eccentric guy called "The Doctor" who has a British accent and is actually a 900-year-old alien being known as a "time lord" who travels back and forth in time using a time machine that's disguised as an old-fashioned blue police box called the TARDIS (Time and Relative Dimension in Space) that happens to be bigger on the inside than it appears on the outside. And the actor who plays the Doctor changes every few seasons because every time the character dies, he "regenerates" and changes into a new form.

I love science fiction, but I'll confess that at first, the concept sounded a little too weird, even for me. However, it only took a few episodes for me to fall in love with this show. It's one of the quirkiest, wittiest, and most creative and imaginative shows on television. The BBC show — which is celebrating its 50th anniversary this year — seems to be constantly reinventing itself, and I think the reason it continues to appeal to fans is that it always feels both "fresh" and "familiar."

Although the show traditionally has been more of a cult favorite here in the United States, I'm excited to see it increasing in popularity lately. The Doctor recently made the cover of Entertainment Weekly and TV Guide, and more and more people are tuning in to the episodes on BBC America.

Running for 50 years is an impressive feat for a TV show, especially since most series are canceled after a few seasons. However, despite its fairly stable popularity, "Doctor Who" has had its rough periods, and the show almost disappeared permanently in the 1990s after a period of declining popularity. A TV movie in 1996 failed to restart the series, but the BBC thankfully didn't give up, and in 2005, the show returned with a successful reboot starring Christopher Eccleston as the ninth Doctor.

So far, there have been eleven reincarnations of the Doctor, a character most recently played by Matt Smith. I have a T-shirt that has a picture of the TARDIS and says "You never forget your first Doctor," and I think that holds true for many fans. :) Everyone has their favorite Doctor, whether it's Tom Baker (fourth Doctor) from the classic series, David Tennant (10th Doctor) from the reboot, or one of the other "regenerations."

Although each of the Doctors have good characteristics, my personal favorite Doctor is David Tennant. Tennant is able to perfectly capture all the nuances of the character. The Doctor is eccentric with a quirky sense of humor, and he's incredibly smart (though unlike another famous character from a BBC show — Sherlock Holmes — he doesn't put others down for not being as quick-witted as he is). However, the Doctor also has a certain sense of darkness and sadness. He quite literally has the weight of all of time and space resting on his shoulders, and as the last of the time lords, he's also forever doomed to be lonely. He has companions that travel with him, but in time each one either chooses to leave the TARDIS or is pulled from the Doctor's life by a tragic event.

While I'm most familiar with the rebooted series, which has run for just seven seasons so far, it's still tough to pick out my favorite episodes from so many good ones. You really do never quite know what to expect from the show. After all, what other science fiction show has a plot like this: dinosaurs, ancient Egyptian queen Nefertiti, and a fedora-wearing adventurer who bears more than a passing resemblance to Indiana Jones, all running around on a space ship? ;)

My all-time favorite episode is probably the two-parter "The Empty Child" and "The Doctor Dances," starring the ninth Doctor Christopher Eccleston. The story is set during World War II and features a creepy zombie-like hoard of people wearing gas masks. It also introduces one of my favorite recurring characters in the series, the swashbuckling con man Captain Jack Harkness. Another one of my favorite episodes is "Blink," which features David Tennant. Although the premise — stone angel "statues" that only come to life when you look away or close your eyes — doesn't necessarily sound all that scary, trust me, after you watch it, you will never again walk by those stone angel lawn ornaments in the gardening section of the store without flinching (and you definitely won't blink). ;)

So, what will the next 50 years bring for "Doctor Who"? Fans have been speculating whether eleventh Doctor Matt Smith will be regenerating at the end of the current season, and who will play the Doctor next. There have been plenty of rumors: Benedict Cumberbatch, star of the BBC's Sherlock Holmes drama, will take over as the Doctor, or the Doctor will switch genders and be played for the first time ever by a woman. I've also heard rumors that we could be seeing a big-screen "Doctor Who" movie sometime in the future.

Wherever the show heads, I hope it continues to be fun, creative, and thought-provoking. If you haven't seen the show before, I'd encourage you to check it out. And if you are a fan, what are your hopes for the show's future?