- Acting for Two: Colin Baker also provides, uncredited, the voice of a Jacondan at Freighter Control in part three.
- Creative Differences: John Nathan-Turner and Eric Saward had different ideas as to what The Sixth Doctor's debut story should be.Nathan-Turner wanted a straightforward adventure pitting the Doctor against a strong villain, while Saward felt that the new Doctor's personality would be better showcased in a more unusual storyline.
- Creator Backlash: Director Peter Moffat described this story as the worst serial he ever did. Eric Saward felt the script was lousy, "but it started as a half-decent idea".
- What Could Have Been:
- The original script featured the Jaconda and Gastropods being dropped totally without resolution to the plot, with the final battle taking place in another dimension against a being called Azlan who was controlling Mestor all along.
- Ian Levine suggested that Azmael be the Doctor's old hermit mentor, referred to in "The Time Monster" and "State Of Decay". Unfortunately, Anthony Steven misunderstood the nature of the Doctor's relationship with the character, and made him a tutor at the Prydonian Academy instead.
- John Nathan-Turner was encouraged to cast two more experienced female actors as Romulus and Remus, but chose male actors because he believed it was crucial the characters be boys for the script to work. He may have had a point about this (the twins can be read as a Plot Parallel for the Doctor's fragmented personality following his regeneration).
- Peter Capaldi was considered for Hugo.
- Jim Broadbent was considered for Drak.
- Peter Cushing was considered for Edgeworth.
- Working Title: A Stitch in Time and A Switch in Time.
- You Look Familiar:
Trivia / Doctor Who S21 E7 "The Twin Dilemma"