- Cast the Runner-Up: Bernard Padden auditioned for Adric, but lost out because of his strong Northern accent. (At the time, it was felt that an extraterrestrial character should not have a distinctive accent - apparently not all planets had a North back then.) Instead, he appeared as Tylos.
- First Appearance: Of Adric.
- Promoted Fanboy: Writer Andrew Smith was a seventeen-year-old who achieved his lifelong ambition to write for the show. He submitted several further scripts to the production office, none of which were made, and eventually became a police officer; however, he had a Career Resurrection in 2010 when he started writing scripts for Big Finish.
- Reality Subtext: Adric's brother dies in this story. Matthew Waterhouse's brother committed suicide when his proposal was rejected.
- What Could Have Been:
- In Andrew Smith's original outline, the adventure involved the TARDIS landing on the planet Alzarius, where monstrous Marshmen rise from the swamps during the time of Mistfall. As the Doctor and Romana explore, a space freighter crashlands on Alzarius, and the time travellers must help its crew repair the ship while fending off the Marshmen and gigantic cave-dwelling spiders. They are aided by a young Marshchild, who has been rejected by the rest of her kind due to her pacifist nature. In the end, the Marshchild sacrifices herself to keep the Doctor and Romana safe until the mists vanish and the Marshmen retreat to the swamps.
- A power struggle amongst the Outlers between Varsh and Tylos was eliminated from the script, while a Marshchild character was reintroduced, replacing a mature Marshwoman.
- Originally, Adric's knee was mended by that the Doctor provides.
- Dexeter was originally named Lexeter. This was changed to avoid confusion with Lexa in "Meglos".
- Varsh was originally named Arfrus.
- BRIAN BLESSED, Donald Houston and Edward Woodward were on the shortlist for Login.
- Michael Sheard was considered for Dexeter.
- Working Title: The Planet That Slept.
Trivia / Doctor Who S18 E3 "Full Circle"