The Mysterious Planet

Notes

• The actor playing Merdeen, Tom Chadbon, had previously appeared in the classic 1979 Doctor Who story City of Death starring Tom Baker as Fourth Doctor.
• The uncredited actor inside the Drathro costume is Mike Ellis, father of Blue Peter presenter Janet Ellis and grandfather of Brit-Pop songstress Sophie Ellis-Bextor. Janet Ellis had previously appeared in the 1979 Doctor Who story The Horns of Nimon.
• The opening model shot of the Time Lord Space Station where the trial is held throughout the season was the most expensive model shot from the classic series run (costing more than £8,000). The sequence depicts the Time Lord Space Station orbiting in space then dragging the TARDIS inside via the use of a tractor beam.
• Dominic Glynn was hired to score the music for The Mysterious Planet, and John Nathan-Turner offered him the chance to rearrange the opening title music. His new score for the opening theme was the shortest lived, lasting this season alone (not counting Paddy Kingsland's 1973 version, which was never even used). Some saw it as an improvement on the Peter Howell version, while others criticized it for being "too quiet" or "not scary enough". It has since been used on the majority of the Big Finish Productions audio plays featuring Colin Baker as the Sixth Doctor.
• From this serial onwards, all location work would be recorded on Outside Broadcast (OB) tape instead of 16mm film. The BBC had been encouraging the replacement of film cameras with OB cameras since the early 1980s on the grounds that they were cheaper, and mixed with studio-shot material better.
• In this serial the First Law of time refers to non-interference, as opposed to a Time Lord meeting a past or future incarnation as stated in earlier serials.