Jim and Edith walk in front of Floyd's Barber Shop, the same building adjacent to the sheriff's office of Mayberry, NC.
Rollin Hand, posing as a Doctor, orders "5 cc's of Cordrazine" for Raymond Barrett. This is the same fictional drug with which Dr. McCoy is accidentally injected in the episode "City on the Edge of Forever".
The use of the Guardian of Forever causes Spock to be replaced as first officer by an Andorian
A Starfleet officer refers to 20th century technology as "stone knives and bearskins."
Episode is named after this episode of Star Trek, on top of that someone wears the same outfit from Star Trek.
Episode mentioned by Mark in his office when talking to William Shatner. Also mentioned by Mark at Robert's apartment.
The cast of Star Trek appear from the time portal from this episode, also Shatners final line "Let's get out of here"
Frasier buys Noel Joan Collins' wig as an apology gift
A replica of the Guardian of Forever was displayed at the Minnesota convention.
The Gateway to the past appears again
Alana mentions Edith Keeler, McCoy uses cordrazine on Sulu again.
The Guardian of Forever causes another time paradox
When Sheldon dreams he's on Vulcan, the Guardian of Forever appears in the background
Mentioned in dialogue.
A clip from 'The City on the Edge of Forever' is shown in 'Cosmic Thoughts'.
Brief clip of Joan Collins shown
Episode is a parody of this episode of Star Trek with JFK in place of Kirk's love interest.