There is a special encounter in which you come across a stone ring called the "Guardian of Forever."

If you pass through it, you are instantly transported into Vault 13, where you can find good loot, as well as come across a Computer Terminal with a "functioning water chip." You cannot leave this area until you interact with the computer. Doing this will make you accidentally break the Water-Chip giving you 1000 exp and the message "You have broken the water chip... the vault has maybe 100-150 days left of water. This comforts you for some reason."

This is a reference to the Sci-fi series Star Trek, specifically referencing the episode The City on the Edge of Forever. In it, Kirk, Spock and Doctor McCoy are transported into pre-WWII America and cannot return home until history is fixed, with the stone ring acting as a portal into the past.

This also suggests that the player (The Chosen One) is directly responsible for the beginning of the first Fallout game, in which the player (The Vault Dweller) has to go out and look for a new Water Chip to replace the broken one, having only about 100-150 days to do so.