Season 6 episode 12, overclockwise. What was written on the paper Bender gave Leela and Fry that said what would happen if they ended up together?
Everything that would ever happen to them in a relationship sense. It showed their betrayals, good times, sad times, but they found out that they'd be happy together in the long run.
An entire list of events that they would experience from that time to the end of their lives. It appears that they would have many ups and downs which works perfectly for the show since we can assume that each episodes "up" and/or "down" for them is part of that papers answers.