- Missing Episode: A near-unique example for the series; "Planet of Giants" was originally recorded as four episodes, but later the third and fourth were combined into a faster-paced Episode 3 (the unused footage was destroyed). This ended up leaving a one-episode hole at the very end of the Season 2 production block, which was filled by "Mission to the Unknown". The DVD has a reconstruction of the missing scenes, using Carole Ann Ford, William Russell, and soundalikes for the deceased cast members.
- Recycled Script: More of a recycled idea. The basic premise of "miniaturized travelers" was one of the ideas suggested very early on. It would have been the first story, but the series' effects budget wouldn't allow for it at that early stage.
- Working Title: Miniscule Story and The Miniscules.
Trivia / Doctor Who S2 E1 "Planet of Giants"