I'm imagining a sci-fi novel where aliens have extended their own lives but not improved their memory, so after 5 million years they reach their destination doing nothing but singing and merriment on the way. Sadly, upon arrival they can't remember why they are there, where they are from, or anything else important. Maybe all over the ship they left notes to themselves a la "100 years of solitude" but sadly they can't remember how to read them.