For fans of Doctor Who, watching an episode that features a regeneration is always a bag of mixed and complicated emotions. On the one hand, viewers have to bid farewell to an actor and a take on the character they truly love.

A Doctor's final episode is always one to be emotional, and it doesn't help matters that it sometimes feels like you are letting your favorite character go. On the other hand, fans also look to the episode with excitement, knowing this will be the first time they see a new Doctor in action.

RELATED: Doctor Who: Twelfth Doctor’s Cast Looks Back On Their Era, Favorite Episodes

There is nearly always a combined sense of sadness and wonder, of heartbreak and discovery. That was once again the case in this year's "Twice Upon A Time."

In Doctor Who's latest Christmas special, written by departing showrunner Steven Moffat, fans of Peter Capaldi's take on the Doctor had to say goodbye to an actor who has magnificently embodied the role for the past three years, and welcome Jodie Whittaker on-board the TARDIS. The announcement that Whittaker would be the next in a line of 13 actors to portray to role of the famous Time Lord was met with both applause and criticism, with love and vitriol. Some fans embraced it as a welcomed change, while others revolted, preferring the series to maintain its long-lived status quo. But Doctor Who has always been a show about change and acceptance, which makes the 13th Doctor an obvious, natural progression for the long running sci-fi series. And already, we can see that Whittaker's 13th Doctor will fit right in.

RELATED: Doctor Who: In Defense of the 13th Doctor’s Outfit

Although she didn't get much screentime in the holiday special, we did catch long enough of a glimpse to see that Whittaker genuinely belongs inside the TARDIS. With only a single line -- two simple words, in fact -- the character tells us everything we need to know about her. Catching her reflection, realizing that, for the first time in fourteen cycles of life she is finally a woman, she says, "Oh, brilliant," with equal amounts of relief and wonder. It's the perfect way to show fans of the series that this is a change that the Doctor herself welcomes, one that the character may have even been looking forward to.

Doctor Who 13th Doctor Costume

In "Twice Upon A Time," Capaldi's Doctor had to face his own desire to stop regeneration cycle, to die and finally stop running. But thankfully, he decided that the universe truly, always needs a Doctor hopping about it. His change into Whittaker is one that makes sense for the character, as well as the series itself. This is a big shift, an upheaval that will make everything new once again. Whittaker's 13th Doctor recognizes that fact with a simple look in the mirror. We don't yet know what kind of Doctor she will be, but we already see know that she will be the Doctor. She will be different, but like all others before her, she will still be the person who doesn't stop running.

RELATED: Doctor Who: Moffat Offers Advice To Fans About Whittaker’s Female Doctor

The new Doctor's adventures are off to a fiery start, and we just might be looking at a grounded Time Lord when the show returns for its eleventh season. With the TARDIS in flames and Whittaker's Doctor in the midst of a free fall, we witness the introduction of a Doctor that is slightly reminiscent of Matt Smith's arrival on the show. And just like Smith's, the new Doctor arrives with a clean slate -- no companions, no sonic screwdriver, and a broken TARDIS that will, once again, change. This is truly a new beginning, and we have a feeling its going to be... brilliant.