Knock, Knock

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"Knock, Knock"
Real Ghostbusters episode
Knock Knock Title.jpg
Episode no. Season 2
Original air date November 6, 1987 (1987-11-06)
Episode chronology
← Previous
"Moaning Stones"
Next →
"The Spirit of Aunt Lois"
Real Ghostbusters: Season 2
Real Ghostbusters: Episode Guide

Underground construction workers come across and open a door that was not meant to be opened until Doomsday. The Ghostbusters race to close it before the world really does end.




  • The title of this episode is a reference to the form of joke, a Knock Knock joke.
  • The reference of Egon being able to speak Sumerian is a nod to the first Ghostbusters movie. Gozer was a Sumerian god.
  • A manhole cover in the episode says "Aija-Do", a Japanese animation company.
  • This episode utilizes several sound effects from the Star Wars films, including a laser blast and lightsaber activation, deactivation and humming sounds.


After Peter backed away from a pink-haired, skull-faced ghost.

Peter Venkman: Say, now when was the last time you saw your dentist, hm?

After narrowly saving the world.

Peter Venkman: That was great. Can we do it again?
Doomsday Door: Do Not Open Until Doomsday!
Peter Venkman: It was just an idea.

Referring to the writing on a stone tablet.

Egon: It's Sumerian.
Winston: Can you read Sumerian?
Egon: In my sleep. Underwater with the lights off. Of course I can read Sumerian.