 Chris Bentley notes that two guest puppets make more than one appearance in the episode.The puppet that plays Shroeder in the flashback to "Crater 101" and a puppet that plays one of the police officers in the flashback to "Big Ben Strikes Again" also have non-speaking roles in both the Markham Arms scene (as the pianist and a patron, respectively) and the extract from "The Trap" (as two of the conference delegates).A similar observation is made by Jim Sangster and Paul Condon, authors of "Collins Telly Guide", who compare the appearance of the Shroeder puppet to that of actor Robert Mitchum.