Fallout 3

Trivia: Megaton: There is a character guarding the gate named Stockholm off in the distance located in a spot that you're not supposed to be able to get to. But through a series of item manipulations and jumping along borders of buildings and obstacles, it is possible to reach this character and talk to him. When you do, he actually has a funny line that the developers put there in the off chance players did manage to glitch their way to this inaccessible character. "The more time I spend talking to you, the less I'm spending watching for raiders... How the hell did you get up here anyway?"

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