- 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 Nightmare Fuel 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.
- 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 Team Pet, 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 Evil Twin 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 Adaptation Decay 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.
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 Spock Speak, 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 Extreme Ghostbusters.
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.
- This would also explain why Egon seems to be a little more interested in romance than he is in the movies (seen in episodes like "Janine, You've Changed"). Peter is a hopeless romantic, so his mind would be inclined to add romance where there previously was none.
One episode had a Freeze-Frame Bonus 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".
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.
Ghostbusters II never actually explains when or how things ended between Dana and Peter, so chances are it happened in the period of time between the first movie and the show, with Peter unconsciously sabotaging it due to his fear of commitment. Dana says in the second movie that the two parted on bad terms and lost track of each other, so that explains why Peter never brings her up - he's trying his damnedest not to think about her, still smarting over how badly he's screwed up.
- Alternately, she isn't in the cartoon because she doesn't exist as such. The movies are Hollywood's version of the events that the Ghostbusters went through. It would be typical of them to include a composite character, and even shoehorn in a romantic subplot with little or no basis in reality.
At the end of "Xmas Marks the Spot", the Ghostbusters hear a voice which could be Santa but they say it probably isn't. "Elementary, My Dear Winston" establishes that if enough people believe in a character, an apparition of them may appear. Perhaps there's one of Santa.
In the "Slimer" shorts, there exist anthropomorphic animals, which don't exist in the series proper. The episode "It's a Jungle Out There" featured a demon named Ral, who wanted to make animals sapient and have them take over.
In the "Slimer" short "Dr. Strangedog", an anthropomorphic dog wanted to make dogs take over and humans be pets, which sounds eerily like Ral's plan. Perhaps he was behind all the anthropomorphism, and the "Slimer" shorts ended when he was trapped for a second time.
The animals' ability to survive being thrown through the air, run over by cars, etc. could also be explained by them being possessed — it's supernatural immunity.
Yes, Slimer is a ghost, but episodes like "The Two Faces of Slimer" show that he can sleep. Dweeb is real (as shown in "Deja Boo") and so are the Ghostbusters and Janine, but the rest of the characters in those shorts are just Dream People, hence the cartoon physics not present in the series proper.
It would also explain why the animation is different, since often in dreams, things are a little "off", and why he's the lead character, since he's the one dreaming. It would also explain him having his own bed (since maybe he wants to have his own bed) and the existence of a non-existent flu in "Nothing to Sneeze At".