Theory:Doctor Who television discontinuity and plot holes/The Star Beast

• So the one way to fix the metacrisis is to just let it go, and Donna gets to keep her memories. Why didn't she just do that in Journey's End all those years ago?

She has the benefit now of a) more time to think about it, compared to the first time the crisis started to hit, when she had seconds to consider whilst being increasingly unstable, b) fifteen years more wisdom and maturity, and c) a different perspective, with a family of people she loves and who support her, rather than having just lost her father, feeling purposeless and undefined as Donna, not helped by the poor relationship she endured with Sylvia the first time around. Giving up being "The Doctor-Donna" now is just surrendering a part of her identity to preserve all that; fifteen years ago it would have seemed like giving up everything that mattered.

• How exactly does Donna's metacrisis work? You'd think Donna would only have the Doctor's mind up until the point when she originally gained it during the metacrisis (the mind of the Tenth Doctor and preceding incarnations), but she seems to know his future or at least that he was a woman, something that hadn't happened to the Doctor by the time she gained his mind. Does this mean that Donna gained new incarnations mind's as part of the metacrisis every once and awhile? Or that she gained new parts of his mind once the Doctor reawakened the metacrisis in her? Or something else entirely? Does this also imply that other metacrisis beings that happen to have the Doctor's mind (like the Metacrisis Tenth Doctor) also subconsciously gain memories of the happenings of the regular Doctor?
  • This would somewhat be explained in the next special, Wild Blue Yander, as Donna is indeed confirmed to have access to all the Doctor's memories even ones he hadn't experienced when she took on his mind, however, she's unable to access most of them.

• How does Rose's age work? Apparently, she's 15. But it's only been 14 years since Donna stopped travelling with the Doctor (yes, I know they SAY 15 years in the episode, but it's actually only 14 because of the the whole 12 months later Aliens of London thing). If you then throw in the End of Time happening ANOTHER year later (and Donna not being visibly pregnant), meaning the EARLIEST Rose could be born in summer 2011, meaning Rose should be MAXIMUM 12, which she clearly isn't (I know Russell T has said he deliberately messed with the timelines a bit in order for him to cast Finney who was 18 at the time, but that's an out of universe explanation, not an in universe one)
  • Technically Russell T. Davies also somewhat gave an in-universe though he was mostly joking. The in-universe explanation makes mention of a time cloud that descended over Camden and dislocated everyone by exactly eight months and three days. That said, it most likely shouldn't be taken too seriously and even if it was meant to be taken seriously, Rose would at most be 14 not 15.
  • Rose could have been adopted at an early age. Maybe the baby Donna was pregnant with was given up or didn't make it.
    • If that would be the case Donna would have died after the Doctor reactivated the DoctorDonna and Rose would not have had everything passed on to.
      • That relies on an overly literal, biological reading of the Metacrisis "passing down". It's a supernatural essence, not a blood disease; it's biodata-based and could very plausibly pass on via a ritualistic combination of emotional closeness plus prolonged proximity.
• Why is the TARDIS damaged so much by COFFEE? And, if it was POSSIBLE for it to be damaged to that extent, WHY would it out a coffee machine on the console?

She wanted to test out her new cloister bell and have a good long run to stretch her engines at top speed after her refit, so put the coffee machine on the console in order to give herself an excuse.

• Why is Shirley Anne's wheelchair equipped with darts and rockets for emergencies but not a motorised engine? Surely, in a situation that would require her to use such weapons, she would also need a motorised wheelchair to allow her to get to safety quickly and out of danger.
  • Because she is a person with free will and chose not to or maybe just didn't think of it.

Perhaps it's an either/or choice; the power unit and ammunition storage and mechanism for the armaments may not leave enough room or weight allowance for a motor as well.

• How do the cracks on the Earth reseal itself as if nothing has happened? We can clearly see some bricks falling through the cracks.

Perhaps the double dagger drive has a temporal drive element to it; or, at least, uses technology that one-and-a-half Time Lords, working together, can turn into a rudimentary one in order to undo the damage it was doing to Earth; hence, the cracks were "un-happened" when the power was reversed. Either that or at least one alien invasion has left Transport for London in possession of some very efficient street maintenance nanotech.