In his former life (circa early 80's) as an ORIGINAL GHOSTBUSTER (OGB), Egon spearheaded anti-ecto innovation, and demonic interpretation.
A man of science uncomfortable in the less predictable "real world," Egon is adrift in the 90's... living in the OGB's unkempt, one-time HQ - the FIREHOUSE - endlessly transferring his "Spengler's Spirit Guide" to CD-ROM, and sporadically lecturing at New York Community College
Egon is the little mentioned and little known about Ghostbuster. If Ray is the "heart", then Egon is the backbone of the Ghostbusters. Without his scientific knowledge, the Ghostbusters would have never came into being. We get very few opportunities to see into his persona, the biggest being his love of candy bars. Most of the scenes involving his "secondary" love interest, Janine, ended up on the cutting room floor. "Most of the Janine and Spengler scenes were shot but, ultimately, their romance was not really close enough to the crux of the film for us to spend a lot of time on it." Harold Ramis said in Making Ghostbusters. "I think the audience got a slight hint that there was something going on between them and that was enough."
Here are some classic pictures of his. Click to enlarge: