When Peter, Egon and the rest of the living people escape Boo York and are returned to New York, one of them is a woman in an old fashioned flight suit. This is presumably Amelia Earhart whose actual disappearance has never been explained.
Ray comments about (compared to New York's turbulence; brought on by the vortex) how Chicago, Illinois is the "Windy City." Harold Ramis, Walter (Vladimir Pavel Maximov) Koenig, Bill Murray and Brian Doyle-Murray all hail from there.
The Flip Side world seems to have a dislike for the living Egon Spengler. The Peoplebusters' logo has Egon in it. An image used to scare an Elvira look-a-like's hair straight is a picture of Egon.
Interestingly enough, no Winston Peoplebuster was shown in the episode.
Not all of Boo York's accidental visitors are from New York, the woman in the aviator's cap is most likely Amelia Earhart. There is a man in a suit that might be Jimmy Hoffa.