An SCP that appears as an unremarkable, somewhat out of shape, vaguely Italian, plumber or carpenter that speaks with a Brooklyn accent.
He is not so much kept at SCP HQ, but works there for modest pay. He keeps the whole place running, and is able to repair even the most apocalyptic damage caused by other SCPs. If asked a question on how to fix something he replies in a friendly and professional matter, but will often list components that do not exist.
(example: "What, you guys don't have a Quintonium meta-calibrator? Ah, I guess you gotta special order them things. Don't worry, I ya can get it for ya.")
Mr. Fix It is also willing to offer advice on dealing with more troublesome SCPs.
(ex.: "Okay, so ya know that lizard thing, what cha' call it? Here's how ya fix 'im. Yous gonna need three, maybe four, other thing-a-ma-bobs: 1, da Rulebook. That's got the rules of the universe inside o' it. It's gonna look like one of them composition notebooks, ya know the black and white ones? Yeah those. 2. The Perfect Eraser. It erases anything. Even the cosmic ink that the rules of the universe are written in. 3. Some cosmic ink. Works with a regular ball point or a quill if ya got one. You can pick it up some where in the center of the universe I think. 4, and this is optional, but it'll save you a lotta time. The magic bookmark. You put it inna book, doesn't matter where, close the book, think really hard about what page you want to be on, like what info is in it or what you wanna find, ya' know that stuff, and when you open up the bookmarked page, badda-boom, there it is.
So What'cha do is find the rules for this nasty lizard, erase 'em, right in new ones, and boom. he's whatever you want. Same with any of these other wackos you got around here."
The entire point of Mr. Fix It would be to solve problems with other SCPs