Two modern companions have witnessed a regeneration first-hand.
The regenerations each occur at the end of an episode. In each case, the companion knows something is up: Rose’s Doctor warns her that he’s about to change, while Clara, having met several prior incarnations, is familiar with the process. The Doctor changes, makes a nonsensical remark to his startled friend, and crashes his ship as credits roll.
We witnessed the Tenth Doctor’s first minutes in the Children in Need special ‘Born Again.’ However, each new incarnation’s first official appearance begins at the start of the following episode, with the Doctor staggering out of the battered TARDIS. Ten recognizes Mickey and Jackie, though they have no idea who he is, and he has time for little more than “hello” before fainting dead away. Twelve only vaguely recalls his old friends, and stomps around quite a bit before he faceplants in the dirt.
Rose emerges from the TARDIS into present-day London and her family. Mickey and Jackie love her; they’ll do anything she asks, they’ll look after her, and even if everything goes wrong, even if she loses the Doctor and the TARDIS forever, at least she’s home. Clara finds herself in Victorian London. She knows Vastra and Jenny, but they’re not her family; if the Doctor leaves her, she’s lost, far from home with no way back.
When the trouble begins, Rose is on her own. Though Mickey and Jackie have her back, she is the resident alien expert; when the Sycorax drive one-third of the population to rooftops and ledges, she knows she’s out of her depth, and all she can do is hide. Clara, on the other hand, is not alone. She discovers the underlying evil while in the Doctor’s company, and even though she no longer trusts him, she has the Paternoster Gang to back her up. At no point is she solely responsible for her own safety or that of the people she loves.
When Rose faces the enemy, as far as she knows she’s the only chance her planet has.
In each case, of course, the Doctor returns in the nick of time. Rose’s Doctor is all charm, offering a smile and a wink to her and a challenge to the invader. Gallantry follows, a swordfight in pajamas, and Rose is quickly convinced. Clara’s Doctor saves her, as she expects, then quickly dashes off again, leaving the Gang to fight off androids while he engages in philosophy, and running away with the TARDIS before they return. When Clara sees him next, she has yet to regain any of her faith in him.
In the end each Doctor asks his companion to join him again. Rose needs only to know that he still wants her; their shared enthusiasm for adventure is undimmed. Clara, however, says no – until she gets a phone call, and a familiar voice asks her to see her old friend in this new face.
Rose requires almost no time to rebuild her trust. This “new new Doctor” is playful and charming and clearly values her. By the end of his very first episode, she is ready to run away with him again. Clara, however, finds little of her kind friend in this harsh new form. Resolutely she keeps one foot on Earth, with her home and job and new relationship, and keeps up traveling in the TARDIS only on her terms. Her relationship with Twelve remains prickly and uncertain all season, and only now, in S9, might she finally get the chance to enjoy herself the way Rose did in Series 2.
We can only hope this season is as much fun as that one.