Oh Shit! is a quest in Fallout: Brotherhood of Steel. It is located in the Secret Vault Laboratory Core.
When the Initiate defeats Attis for the second time, the latter explodes and decomposes into a strange organic biomass, a rapidly-multiplying multicellular organism that covers the entire laboratory section of the Secret Vault. This new creature begins to grow with each second, and its various organs, like eyes, mouth, and tentacles begin to appear out of the floor.
To exit the lab core, the player must defeat the blob. The tentacles can be destroyed, but the eyes are really its weak points. Just shoot the tentacles until the eye opens. Shoot the eye until the health bar is depleted. This should be done several times. Destroying the eye will grant the player 600 XP. Now the player can attack the blob's mouth which is the main target of the quest. It can bite but its main danger is its ability to inhale and chew on the Initiate, dealing massive damage. Destroying the mouth grants another 600 XP and clears the path to the exit.