"All You Wanna Do" from Six came to mind - the words don't change that much, but the character's outlook about them sure does. Also, "You Don't Know - Reprise" from Next to Normal ends with the sudden realization about how much Dan and Diana are really sharing with each other.
"I think that when a movie says it was 'based on a true story,' oh, it happened - just with uglier people." - Peanut Walker, Shucked