The scene in which Turlough saves Peri from drowning was disrupted by a German nudist, who thought that Nicola Bryant was actually drowning. After the man learned that she was just acting, he was very unhappy about it, and later ruined a take filmed on the beach by running through the shot.
Writer Peter Grimwade was furious at the casting of Dallas Adams as Prof. Foster. He had written the part for an elderly man and this casting caused Grimwade to cut his links with Doctor Who.
After filming in Lanzarote wrapped, the cast and crew returned to London to film The Caves of Androzani: Part One (1984). Unfortunately, while Lanzarote was summery, the temperatures in London were freezing cold. As Nicola Bryant had to wear the same summer outfit she wore in this episode, she fell ill with pneumonia and frostbite during filming.
The script originally contained commentary on issues of religious zealotry, something that was toned down by Eric Saward.
This is the only televised Fifth Doctor story not to visually contain Tegan Jovanka. The Doctor's reference to Tegan at the beginning of part one means that she was technically a part of every single one of his television stories in some way. To date, the only other companion to have been a part of every televised story of a given Doctor is Doctor Who (2005)'s Rose Tyler, who appeared in every episode during the Ninth Doctor era (though actor Christopher Eccleston only made a single season of 13 episodes as the Ninth Doctor before deciding to leave the series).