Pairing: Izzie Stevens/John Winchester
Fic Title: How to Fix Things
Link: How to Fix Things
Rating/Warning(s): PG-13 for language
Genre: Crossover, (a bit) AU, Angst, Drama
Why This Must Be Read: As both characters were played concurrently by the same actor, there are several fics where Denny Duquette actually is John Winchester. This, in my opinion, is one of the best. John's POV on being Denny and himself and both at the same time, while falling for Izzie and trying be strong enough to be there for Sam and Dean. Short but evocative, set late season 1 Supernatural/season 2 Grey's, with an ambiguously happier ending than both.