WARNING! THERE MAY BE UNMARKED SPOILERS!
- Franchise Original Sin: This episode, along with its predecessor, is very much a prototype of the sort of storylines that Steven Moffat developed during his time as showrunner: There's River Song, the Doctor as an invincible mega-genius and the most important person in the Universe (who is apparently so scary that he makes barely sentient living shadows go Oh, Crap! and run away), and a complex and multilayered storyline with multiple plotlines and character arcs happening at once. It's considered one of the best, if not the best RTD-era New Who story, and for good reason, but for those fans who consider Moffat's tenure a step down in the show's quality, this storyline, for better or for worse, is pretty much where it all started.
- Harsher in Hindsight:
- The episode ends with River Song making a Heroic Sacrifice. At the time, it's pretty sad, but we don't really feel much connection to her since she'd only just been introduced. But as the show continues, we find out more about her and her relationship with the Doctor, and that first episode becomes simply heartbreaking to watch... especially once you realize the Doctor himself should have mourned her death far more than he did, it was just unlucky chance that he didn't know her when she died.
- While in the mainframe, Dr. Moon causes Donna to forget her reality with the Doctor, going around with a seemingly normal life but a lingering sense that something is off and knowing she's forgotten something. After Donna gets mind-wiped in "Journey's End", her life for the next 15 years ends up resembling the virtual reality life — an overall sense of happiness, but with the lingering feeling that something is missing and knowing she's forgotten something.
- Heartwarming in Hindsight:
- Donna is heartbroken to lose her children and husband, even if she believes they weren't real. Over a year later in "End of Time Part 2" she did manage to get married, and 15 years later in "The Star Beast", she is shown with a daughter and a husband who adores her, just as Lee did.
- The DVD writer commentary indicates that in the first draft of the script, Lee would have been revealed to be transgender (assigned female at birth). Donna ends up having a transgender daughter (assigned male at birth) in canon in "The Star Beast".
- River talks about her final night with her Doctor to see the Singing Towers of Darillium. "The Husbands of River Song" reveals that night to have lasted 24 Earth years.
- Hilarious in Hindsight:
- Cal refers to the cyberspace where River is saved to after her Heroic Sacrifice to rescue everyone as "a good place".
- In 2021, WandaVision also featured a married woman in a false reality viewable on a television, who had two children in a drastically accelerated manner. Although in this instance, the woman in question used magic to manufacture this for herself. Whereas the false reality in this episode was manufactured for Donna and thousands of other people without her knowing.
