During the first assault of the Robot Rebellion, Mainframe got caught and trapped within the Joe base computer room, and lost his right arm in the process. Determined not to let it deter his goals, he reverse-engineered a captured B.A.T. and was able to use its technology to create himself a cybernetic arm, which he could attach various weaponry to.

He has since changed his codename to Strongarm.

When I read about the Robot Rebellion group project, I instantly wanted to do a Strongarm custom, because my favorite Joe has always been Mainframe.

I knew I had a broken arm or two in my parts bin, and that's where I started. I got some weird black weapon accessory which fits right into the arm peg, and things got fast from there.