"On a lighter note..."

What are some examples of a very dark album (lyrically and musically) throwing in a much lighter (by comparison) song? For example, Alice Cooper's Brutal Planet is full of dark songs lamenting the state of the world, but mixed in with all that is the more humorous "Its the little things". One could argue "Planet Caravan" on "Paranoid", a softer track about "traveling the universe" coming right after "War Pigs" and the title track, and right before "Iron Man".