Fallout 3 is one of the first, if not the first, game to allow yourself to play your character when they are but a 1-year-old infant. The player is meant to be confined in a small area for this portion of the game, but need not be! This two-part video with instructions will show you how to escape the confines of your father's apartment and wander the games entire world map while still a baby! You will not be able to do many of the game's essential functions (you are a baby) but this is still loads of fun to play around with.
From the creator:
Let me make sure everyone understands what I did. I was able to exit the vault by closing the door before Dad steps in and starts talking which leave the door behind him open and he has to reopen the door before the other door slams shut, but by then I'm already past it. I then jump out a door into a void which sends me near the last part of the Vault, I then steal the key and password from the overseers office. I then leave the vault and walk to Megaton where I'm now able to use the third person view. But you still can not use your pip-boy. You now appear full grown, but you are short as a baby. Because you are too short, you cant really play the game like this, Its more for just messing around with it lol.