“You... My God. YOU ARE THE ONE.”
Jeff Mason, also known as Jeff the Scientist or his title Interrobang, is a worker at Aperture Science on Fiction's Earth in the Destroy the Godmodder series. He is a basic-level employee, though he helped construct the body of Project Binary. Jeff is the protagonist of the Pinary ARG's first game, Jeff the Scientist, as well as the hidden protagonist of 7x7, where he was known as The One. Jeff is apparently very powerful because he is controlled by Nonfiction - the players on the DTG Memo.
Over the course of Jeff the Scientist, Jeff became wanted by the Advanced Superiors due to participating in illegal activities. He was forced into Old Aperture, the ruins of the previous Aperture Science facility, and navigated through a series of intense test chambers known as Project Seven-X-Seven, finding powerful items along the way, including GODHEAD, an artifact containing the powers of the tenth Advanced Superior, Interrobang. He did this to unlock a way out of Old Aperture using the credentials of the Advanced Superiors. Upon Jeff's return, he saw the activation of Project Binary's prototype, Probect Pinary. During 7x7, Jeff traveled through the broken plot of Destroy the Godmodder 2, eventually using red sunglasses to retain his knowledge of all existing universes.
After the events of 7x7, Jeff somehow acquired the title of the tenth Advanced Superior, Interrobang. He traveled with the other Advanced Superiors across the Earth, eventually contacting and fighting against the Godmodder during DTG2's epilogue.
Jeff's credentials are jmasonaperture / anaccentbeyond.
Not much is known about Jeff's life before his recruitment to Aperture. It was stated in Jeff the Scientist that Jeff had originally joined Aperture to help construct GLaDOS, but left the project and the company entirely after he became fed up with how the project was running. As such, he escaped the fate of everyone that saw GLaDOS' activation - death by neurotoxin. Jeff returned to the company once he found that they were hiring, but was unprepared for its changes.
The new Aperture Science was completely controlled by MTT Industries and the Advanced Superiors. Jeff, along with all the other personnel, was forced to live in the facility under constant surveillance by the Superiors. Society in Aperture was strictly divided between levels of clearance - as Jeff was basic-level, he was at the lowest tier. However, he had an important job when it came to Project Binary - he helped build its robotic chassis.
Jeff the Scientist depicted Jeff's activities on the day of Project Binary's activation - the Execution. It began with Jeff in his personal block, contemplating Project Binary until a fateful encounter with Advanced Superior Ampersand. Jeff gave Ampersand some important files and assured him he'd be at the Execution, which was scheduled for 9:01 PM - just a few hours away. Jeff then exited his room, navigating Aperture Science - he knew all the shortcuts and secrets.
After talking with another basic-level employee, Billy, Jeff entered the rec room, which displayed events pertaining to the Second Godmodding War via television. While there, he encountered an advanced-level employee, Johnson Johnson, who told Jeff that he'd worked on coding the A.I., and that its code was unearthly. Six Advanced Superiors, including Interrobang and Caret, promptly entered the room, publicly executing Johnson for playing Minecraft, which was against the rules due to its connotations.
After the debacle ended, Jeff entered a secret area. Originally a hideout for Doug Rattmann, it was repurposed into a room containing an archaic form of the terminal to be used in Project Binary for the enjoyment of basic-level employees.