Possessed Subway Trains were normal subway trains possessed by poltergeist energy.
When the Doomsday Door was prematurely opened, the released poltergeist energy first possessed nearby subway trains and altered its appearance into a sinister monstrosity. When the Ghostbusters arrived at the subway station, it was nearly destroyed during a battle with skeleton spirits. It collapsed onto itself then vanished.
They were last seen when the Ghostbusters used their Proton Packs to pull back everything that was set loose. The poltergeist energy surrounding the trains was pulled back, as well, and the trains returned to normal.
The Possessed Subway Train resembles a screaming angry face with its left eye open and the right eye closed. Its mouth is gaping open with lashing tongue and unleashes primal screams like an animal. It shakes the graffiti off its body which also comes to life.
In another station, another possessed train was vampire-like in appearance with a hook-like face, complete with fangs. It had monsters hanging from it, as it flailed down the station.
A subway train depot was possessed and the remaining subway trains each came to life in equally frightening forms.
The Possessed Subway Trains act bestial and emit growling and screeching sounds.
- In the first draft of the "Knock, Knock" script, J. Michael Straczynski leaves a note suggesting Max Fleischer's "Play Safe" for inspiration on the subway train designs. 
- "Play Safe" was one of the Color Classics animated shorts by Fleischer Studio. "Play Safe" debuted on October 16, 1936.
- ↑ Straczynski, J. Michael (2009). The Real Ghostbusters Complete Collection Volume One Disc Five, "Knock, Knock" Script p. 9. CPT Holdings, Inc. Line reads: "(NOTE: See Max Fleischer's "Play Safe" for some ideas."