[[WMG:The Doomsday Door in the episode "Knock, Knock" is actually a Containment Unit]]
The Ghostbusters themselves seem to have no other manner of getting rid of ghosts other than putting them into the Containment Unit and on various occasions there has been the problem of what happens when all the ghosts get out of the Containment Unit at once and it's not too dissimilar from what happened with this door. It seems like the Containment Unit would have to be kept intact for the rest of time, leaving a problem of how to warn future civilizations. It's a problem that comes up in nuclear waste disposal and it seems to come up with the warning stone and the door itself which says "Do not open until doomsday"
* That makes sense: perhaps the realm behind the door is a pocket dimension that some ancient civilization conjured up to banish the ghosts plaguing their era. It'd even explain that NightmareFuel scene of a skeletal boat captain laughing and ordering his human slaves to keep rowing. Maybe some of the people who created the door got trapped inside when they sealed it shut the first time (just like Egon thought was going to happen to them), and they've been at the ghosts' mercy ever since.

[[WMG: The Stay-Puft Marshmallow Man was recreated inside the Containment Unit]]
The Ghostbusters never "caught" him in any normal sense, but he's inside the containment unit in the cartoon, and somehow he's turned friendly now that, according to Ray, he's not being controlled by Gozer. But how's that possible, and when did it happen? Well, the Destructor was formed by all the PKE energy Gozer had gathered in New York and, when Gozer was dispelled, that energy got released again (causing Stay-Puft's physical form to collapse into marshmallow goop). Then that shapeless PKE energy gradually spawned dozens of individual ghosts, which the ghostbusters hunted down and caught in separate cases over the next several months. Once the last ghost was captured and sent into the containment unit with the others, they all merged back together into the Stay-Puft Marshmallow Man... except, without Gozer's influence, he now has the same friendly personality that Ray imagined he'd have. He's probably also a lot weaker now than he was as the Destructor, but he's still big, strong and benign enough to make him a useful last-ditch option against other ghosts.
* His being weaker now than he was in the movie, and being a pure ectoplasmic ghost rather than a walking, corporeal marshmallow giant, also explains why they can use a trap to release and recapture him. He's not so much the Staypuft Marshallow Man as he is the "ghost" of it.
* There was an episode that explained it in flashback, IIRC it was them telling the story to a reporter of how Slimer became their TeamPet, after killing Gozer they went home, took off their marshmallow covered jumpsuits and tossed them in a box in the basement, where a leak from the containment unit caused the gunk to reform into the animated version of Stay Puff, which they busted, trapped, and stored.
** It formed into EvilTwin versions of themselves rather than Stay-Puft, since the PKE energy took its form from their latent auras. Still, it shows that the Gozer/Destructor PKE energy stayed around after they defeated Gozer, just formless and unchannelled again.
* Another interpretation of this is that the movie was the in-verse adaptation of the "real" event that happened to the cartoon Ghostbusters. So, everything we ''think'' we saw happen in the movie could just be down to AdaptationDecay in the Real Ghostbusters universe version of the movie. The only events that we are ever actually told happened in the Real Ghostbusters version are that they captured Slimer at the Sedgwick Hotel, the containment unit blew up, and the final confrontation with Gozer resulted in them encountering the Stay Puft Marshmallow Man. It's ''possible'' that in the Real Ghostbusters version of those events, the Marmallow Man was actually manifested as a typical ghost that they simply captured in a trap, whereas the 'movie adaptation' of those same events instead interpreted Stay Puft as being a corporeal manifestation that got blown to bits for the sake of condensing and dramatizing the 'real' story.

[[WMG: This is how the individual Ghostbusters made money in the five-year interim between the two movies.]]
This only works by disregarding "Take Two" from the overall canon, but hear me out:
The restraining order forbade the 'Busters from making money while ghostbusting. Nothing said they couldn't become rich beyond their wildest dreams by ''selling'' their story; ''WesternAnimation/TheRealGhostbusters'' is the result. It would probably look more like ''The Original Real Ghostbusters'', with matching flightsuits and a Peter that looks a ''little'' more like Bill Murray at Peter's own insistence; also, instead of Slimer, Mr. Stay-Puft would be the unofficial mascot, after a ProductPlacement deal with the company that produces Stay-Puft Marshmallows. Somewhere around Series 3, the Marshmallow Man starts to take a bigger role, and the show is eventually retooled to focus entirely on him. At this point, we see Movie!Ghostbusters in decline, with Ray and Winston doing kids' parties in a decrepit ECTO-1.

[[WMG: The camera-man has a fascination with Egon.]]
This is something I noticed while I was marathoning the episodes: Whenever the camera needs to zoom in and do a close-up for dramatic effect on any ghostbuster - any ghostbuster at all - the choice is almost constantly Egon. The camera seems mesmerized with his blue eyes in particular.

Now, this could mean a number of things.
* The camera-man has mistaken Egon for the "main" protagonist and is trying to direct the viewer's attention back to him
* Egon's the camera-man's favorite character
* The camera-man has a crush on Egon and this is the only way he/she can confess his/her love
*** Alternatively, Janine has paid him/her for the benefit of seeing more of her beloved Doctor Spengler on-screen
* Egon, by and large, is charged with delivering the show's exposition, complete with SpockSpeak, making him the natural order of focus for the show. Also, the writers may have considered him the main protagonist as well, seeing as how it was Egon that would stay on as the mentor in ''WesternAnimtion/ExtremeGhostbusters''.

[[WMG: Slimer used to be a dog.]]
He certainly acts like a dog, with his short attention span, his general lack of inhibition, and his strong sense of loyalty to the Ghostbusters. It also might explain why he eats so much; he sees being a ghost as his opportunity to finally get to try all the human foods his owner wouldn't let him eat in life.

[[WMG: Peter's parents are divorced.]]
A lot of people assume from lines in "The Thing in Mrs. Faversham's Attic" that Peter's mother is dead. However, lines from later episodes ("My mother reads ''Celebrity'' magazine!" for one.) suggest that she's still living. Possibly, Peter remembers how sad and lonely his mother was when his father ran off to chase the latest Get Rich Quick scheme. She eventually got tired of being in a relationship of one and asked for a divorce. Peter never forgot how heartbroken his mother was. A combination of this plus some missed holidays and visitation weekends further strained Peter's relationship with his father. Mama Venkman is alive and well, lives upstate and tries to find happiness in her present life, but was turned off the idea of marriage. Peter tries to visit her when he can, though his job means he can't as often as he'd like. (He at least manages to phone her on her birthday and Mother's Day.)

[[WMG: The whole show is just Peter trapped in a LotusEaterMachine.]]

Blowing up Gozer's gate and crossing the streams caused Peter Venkman to slip into a version of the world tailored around him. He has become more conventionally attractive, while Ray has become pudgier and Egon looks just plain ridiculous. (He has no opinion of Winston, but only because he barely noticed him and couldn't even remember if he had a mustache.) What's more, his ultimate hustle never ran out of work and he is greeting by cheering fans pretty much every time they finish up a job. The only thing that doesn't fit is Slimer, and he isn't supposed to - That first ghost that "slimed him" is a recurring white rabbit in this illusion world. It represents what Peter must learn and do in order to escape. He starts off wanting to blast the spud, but starts acting friendlier to him as time goes on. The illusion begins to weaken as Slimer's speech becomes more coherent, and Peter begins to sound more and more like Bill Murray.

[[WMG: The Ecto-1's logo ghost is a real one.]]

One episode had a FreezeFrameBonus where the one on the back door winked, and a few seasons later the one on the passenger side was seen to remove the diagonal bar in the episode "My Left Fang".

[[WMG: Egon is either homosexual or asexual]]

Either one could explain why he not only never seems to respond to Janine's interest, but why he never seems to show interest in ANY woman whatsoever. The latter may be more likely and possibly an intentional reference to Nikola Tesla, who died unmarried and possibly a virgin, himself apparently being asexual. Egon can sort of force an interest in Janine if necessary(as he did in "Janine, You've Changed" and in a later ''Extreme Ghostbusters'' episode) if it means saving her but he has to really try to even show that level of interest because he doesn't seem to feel it naturally.