He was involved with many tremendously funny films and wrote what I consider (as does Bill Murray) one of the great Hollywood screenplays in Groundhog Day. Fuss adores him in Ghostbusters. I've never laughed harder than the first time I saw Animal House in the theater.
But my first thought hearing the news was this scene in Knocked Up as Seth Rogan's father.
He's just wonderful, embodying the dream of what you'd like to hear from your dad in that situation.
RIP to a great cinematic talent & splendid man.