Tim is actually and alien from the planet "RATIUG". He came to Earth about 65 years ago with an intergalactic circus of freaks and oddities. Everywhere else in the galaxy, he was considered so grotesque that few could bear the sight of him. When they came to Earth and discovered that everybody here looked more or less like him, they figured Tim wouldn't attract much of a crowd, so they got ready to high-tail it out of here. But Tim saw an opportunity to finally fit in, so he escaped! The circus needed to fill the slot in their galactic sideshow, and seeing that there were even more freakish specimens here, snagged a replacement and left. (The Amelia Earhart mystery solved!)
So Tim just melded into American society as a mild mannered CAD designer and took up playing blues guitar, to which he was remarkably suited, as Ratuigians have 6 arms. How ELSE could he pull off some of those licks! Oh, 4 of his arms are invisible, of course.