- Absentee Actor: Sometimes in Beyond Belief.
- Frank Doyle does not appear in "She Blinded Me with Seance" or "Rosemary's Baby Shower". He locks himself in the (walk-in) liquor cabinet in a fit of jealousy in the former, and does not appear at all in the latter as Sadie is visiting a friend in Detroit. He was also absent in "Romanian Holiday", where Sadie was instead accompanied by Carter Caldwell.
- Similarly, Sadie is absent in the episode "Nuns the Word", where she is at a spa, "Molar Express", where Frank goes to the dentist alone, and "The Skeleton Grief", where she's visiting Donna.
- Actor Allusion:
- Not only does Nathan Fillion once again play a space cowboy (Cactoid Jim), but the character's first appearance was in a Sparks Nevada segment about an author attempting to shadow an officer of the law for research.
- In a later episode, Adam Baldwin guest stars, specifically credited as a "Man from Jim's Past".
- Irony as She Is Cast: Jefferson Reid (ACE AMERICAN) is played by a Canadian.
- The Other Darrin: Some minor characters are voiced by different actors from episode to episode. Pterodactyl Jones, for example, was voiced by Patton Oswalt in his first episode, "The Devil and Mr. Jones", and by Thomas Lennon in the other two, "The Devil You Know" and "Jones on Third". Similarly, Techs the robot was voiced by J. K. Simmons in "The Piano Has Been Thinking", Timothy Omundson in "Marshal on Mars" and Garret Dillahunt in all of Techs' other episodes.
- What Could Have Been:
- Acker and Blacker have said in interview that the original idea for Beyond Belief was about an extremely bitter and alcoholic occult investigator who drank to forget about the death of his True Love. Then they decided to spend some time before the wife's death to really drive home why the character was the way he was. Once they saw how it turned out, including Paget Brewster's amazing performance as Sadie, they realized they could never kill her off.
- Sparks Nevada was originally developed as an animated show for Nickelodeon.
Trivia / The Thrilling Adventure Hour