(When I say change, I mean in-universe, not because of editing and the time in which it was produced.)

For example, the 3rd Doctor's regeneration was a simple fade, and look at regenerations now, they make the head and hands shoot fire as they change. It couldn't be that they're different for each regeneration in the cycle, because if that was the case, the 11th Doctor's regeneration into the 12th wouldn't be the "sneeze", which brings me to my next part.

If the new Who regeneration effect (the fire) was really how it is in universe, why would 11th Doctor's regeneration into the 12th be the sneeze?

  • It is unclear what is being asked here. I will wait for the rest of the community to vote before closing it for lack of clarity. Sep 21, 2015 at 0:08
  • 2
    @Thaddeus I think he's asking for an in-universe reason for why the various regenerations all look different. It's a fair (if poorly worded) question.
    – Rogue Jedi
    Sep 21, 2015 at 0:15
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    I'm not sure what he means by "sneeze", either, but yes, he's basically asking for a canonical answer to "why do they have better SFX now than in 1965?"
    – KutuluMike
    Sep 21, 2015 at 0:26
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    I don't think the question is hard to understand at all. Is there an in-universe explanation for the differences in how regenerations look? However, I believe that John Simm would have more inside information about all that. Anyway, wasn't there a consensus that the Doctor always had difficulty regenerating, more so than the average Time Lord? And I have a feeling that his regenerations became more intense, more violent each time. Then maybe the extra regeneration energy he got from Gallifrey would have helped make it a bit easier again.
    – Mr Lister
    Sep 21, 2015 at 6:54
  • “I mean canonly” — that would be helpful explanation if “canonly” was a word! Sep 28, 2015 at 9:23

6 Answers 6


"Regeneration effects are like a box of chocolates. You never know what you're gonna get." -Forrest Gump

If you want some attempt at a canonical answer, though, the best I've seen is that the first explosive regeneration was

McGann-Hurt, in The Night of the Doctor.

This regeneration differed from all of the previous regenerations in that The Doctor actually had some control over the outcome.

He asked the Sisterhood of Karn to make him a warrior.

Presumably, attempting to influence the outcome of a regeneration results in a more violent transformation that extended to Eccleston's and Tennant's regenerations too.

I'd chalk up the "sneeze" to The Doctor's body still adjusting to

the sudden influx of regeneration energy it received in The Time of the Doctor.


Although it may be a psychological quirk or semi-conscious choice to leave his appearance to chance, the Doctor seems to have very little control over his re-generations in terms of appearance and personality and even appears to enjoy surprising himself with the results, often commenting on his own features out loud. This is reflected by the often apparent lack of control over TARDIS destinations displayed by all his incarnations, each of whom enjoy exploration and adventure.

In contrast to the Doctor, when the Time Lady known as Romana regenerated, she had the ability to playfully try on a few different "bodies" or looks during her regeneration beginning with Princess Astra's likeness, then a vertically challenged blue female, then a buxom red-head and then a very tall lady from ancient Greece before reverting back to Princess Astra's body again: all in the space of a few minutes and without strain or great effort of any kind.

The Master's regeneration style is very demonic in appearance and has even stolen or taken over live bodies for at least two of his later re-generations.

Whilst circumstances before and during regeneration and, of course, the relative condition of the former body (e.g. old, battle-damaged, poisoned, shattered, burned, irradiated, dismembered, etc.) would be a factor in the amount of energy required to regenerate fully and which would also produce a differing effect, it also appears that the psyche is an influencing factor.

SOURCE: BBC Television aired shows and re-runs 1975 to present day.

  • WRT Romana: Noting, of course, that she left the room for each body change. However, as shown the delays between each body's "turn on the catwalk" were quite short. Short enough, in fact, that either the delays were compressed, or she was regenerating clothing as well. Of course, in reality the other actors gave Lalla Ward enough time to change clothes into a mock-4th-Doctor style, but we're talking in-universe.
    – RDFozz
    Oct 17, 2018 at 16:21

There's no in-universe reason why regeneration effects can't be different.

Regenerations are triggered by genes and the face new Doctor gets is fully random (with few exceptions). It can be because some genes randomly dominated one regeneration than other. Regeneration effects can be explained in similar way. If certain genes become dominant in certain way, The Doctor would shoot fire while regenerating, otherwise not.

  • “Regenerations are triggered by genes” — are they? I’m sure you’re right, but was that mentioned in the show? Oct 31, 2015 at 12:31
  • Ah, good to have you back answering DW questions :-) But "the face new Doctor gets is fully random" - is it? Twelve's face definitely isn't random, and nor was one of the earlier ones (Three? Four?). Have we ever had confirmation that most of the faces are random?
    – Rand al'Thor
    Oct 31, 2015 at 12:34
  • This lacks supporting material. Canonically it is established that faces are NOT necessarily random. The Doctor has never been good at regeneration (he repeatedly struggles with it as early as Jon Pertwee and particularly badly with Peter Davidson) but other Time Lords can control their regenerations (Romana) and with number Ten, we get the sense that The Doctor forcibly held back his regeneration for an extended period, because he didn't "want to go". Jun 9, 2016 at 12:46

I'm not familiar with the old series or the film, but, since the "fire" regenerations seem to have begun with war ----> nine, my circle of nerd friends theorize that it is linked to the absence of Gallifrey. Either the planet itself or the untempered schism on it absorb the energy, or the energy is somehow diluted among all the existing Time Lords.


I couldn't give an answer on why the golden Fire is recently the typical regeneration effect given that all regenerations since the show's revival have had the same effect, the only exception being The Master's effect being a more white/red/green colour. However the 'sneeze' as you call it is because The Doctor already repaired and renewed his body at the top of the bell tower with a massive energy burst. His body reset but the cells were still regenerating so the reason it was instant was because all that was left to change was the appearance as the bulk of the regeneration had already happened.

  • 1
    The fire with the regeneration was a result of a misunderstanding. It first appeared with the regeneration of Nine into Ten, but it was not intended to represent part of the regeneration process itself, but rather the vortex energy the Doctor had absorbed and which was killing his body. However, by the time of the next regeneration, this had apparently been forgotten, and they made it part of the "standard" regeneration process.
    – Buzz
    Feb 17, 2017 at 18:16
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    @Buzz do you have a reference for that? Because the references I've heard say that they deliberately made it consistent.
    – Werrf
    Feb 17, 2017 at 21:18
  • @Werrf I don't remember where I heard it from; I think it was somebody who had worked on the show's first season. I suppose that later, in a desire to make the subsequent regenerations "consistent," they may have included the "fire" effect, even knowing it was originally intended to represent something different.
    – Buzz
    Feb 17, 2017 at 21:30

While it can be difficult to come up with an in-universe explanation for something that has an out-of-universe explanation of different effects techniques, and possibly a much better budget, let's try.

TL;DR - We can theorize that the more regenerations a Time Lord has gone through, the more difficulty they have during/immediately after a regeneration.

Looking back to the regenerations from the original series, we see no significant mental trauma or confusion involved in the earliest regenerations. While the 2nd Doctor was different from the first, most of the confusion in his regeneration came from his companions, who simply weren't entirely sure this was the same person. That element didn't really come up again, from what I've seen (he had active companions during the regenerations from 3->4, 4->5, 5->6, 6->7, 9->10, and 11->12, at least).

Starting with the 4th regeneration, into the 5th Doctor, we started to see significant mental issues - calling people by the names of old companions, and the like. While the regeneration into the 5th Doctor seemed the worst (and the Master may have had something to do with that), the 6th and 7th Doctors both showed some confusion and distress at first (haven't watched the 8th Doctor movie recently enough to recall - but he did say he was part human then, which has basically been disavowed by now, I believe).

Something unique to the 4->5 regeneration was the Watcher - who was, apparently, the Doctor in a state in between his 4th and 5th forms, bouncing back in time to "watch" the 4th's last adventure. This can be handwaved away for any of a number of reasons - his visit to Logopolis and its unique nature, and the possibility of the Master's involvement in order to manipulate him into going to Castrovalva being the two that leap to mind.

Starting with the War Doctor, we've seen a certain amount of physical trauma as well, in the form of the regeneration fire apparently causing the physical change. I haven't seen the regeneration into the 12th Doctor yet, but the explanation that the majority of the change was accomplished earlier, and the "sneeze" just adjusted the cosmetics, seems roughly credible to me. (I think we were also told that the Doctor had been putting the full regeneration off for some time, leaving his 11th form to limp along after it should have been replaced, which could account for some special oddities here.)

(That said, the idea that the regeneration from 9 to 10 wasn't using the fire as a standard regeneration technique, but as something caused by the Vortex energy, also seems entirely credible out-of-universe. And, so does the idea that, whether due to the team involved forgetting that fact, or simply due to the "coolness" factor, this became a part of the standard regeneration).

This leads to a logical (though not explicitly stated in canon) theory that the older a Time Lord is (or the more regenerations they've gone through), the harder a regeneration is on them.

I should note that I believe there are two regenerations that happened off-screen: the regeneration from the 2nd Doctor to the 3rd, and the War Doctor to the 9th.

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