For a game that's meant to be taken slowly and can take upwards of 100 hours to complete, a 24 minute completion time for Fallout 3 seems impossible.
Well it's not, as YouTube BubblesDelFuego has discovered. He's so happy with the run that he's not going to challenge it unless "something big is found" or someone else tops it.
Given how tedious this speedrun looks to execute, there probably aren't too many competitors gunning for the prize. But you never know. It's a jungle out there.