There's a sequence in the episode "Statue of Liberty" in which: The Ghostbusters go up a reeeeeally long flight of stairs (sound familiar?) in pursuit of Mysteria. Mysteria catches up to Eddie and surrounds him with mist. Eddie falls, and Tracy uses the Ghost Gummer to catch him in the nick of time! The sequence was reused in a later episode, replacing Mysteria with a generic orange ghost!
What Could Have Been: In the original "series bible" (the document which lays out the vision of the series), the moronic Airhead was described as working for the Ghostbusters while serving Prime Evil—in other words, a mole. This gave his incompetence a very interesting angle, but in the finished series, he was just a moron.