Knock, Knock

{{Infobox television episode
| Title = Knock, Knock
| Series = Real Ghostbusters
| Image = <!-- image: Knock Knock Title.jpg -->
*200px*
| Season = 2
| Episode = 
| Airdate = {{Start date|1987|11|6}}
| Writer = 
| Episode list = [[Real Ghostbusters: Season 2]]<br/>[[Real Ghostbusters: Episode Guide]]
| Prev = [[Moaning Stones]]
| Next = [[The Spirit of Aunt Lois]]
}}

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.