Morpheus, a dream-demon, is making everyone in town have nightmares involving something that they are afraid of.
Eduardo loses his hair after Kylie rejects him...
In Egon's nightmare, he's walking naked through town, with everyone either laughing at him, whistling at him suggestively, or reacting ion disgust, and when confronted by Morpheus about his nudity, rather then freak out he says, "Hmm. Fascinating. I seem to be experiencing a nuero-soboriphic event...with distinctly Freudian overtones." He's too analytical even for his dreams.
Eduardo's reaction to being told the consequences of crossing the streams in "Darkness at Noon".
"Keep it up Garrett! You STINK!! PERIOD!!"
In "Fear Itself" we find out that Slimer's fear is a plate of vegetables. The sight of him screaming in terror when confronted with broccoli is hilarious.