He taught multiple subjects while there and tutored Marge. Marge fell in love with him and eventually started to imagine Homer as him.
Marge left Homer for Stefane and they started dating until Marge found out he didn't want to get married at all and that he was actually not at all like her.
In the last scene where he sees Homer and Marge kissing while he's walking the dog. Disgustingly, he call them "townies" before walking away.