Fake Nationality: He's stated in interviews that he can do any accent he can get paid to do. Irish, Italian, French, Russian… The Dresden Files audiobooks pretty much prove that.
He is a Dragon Ball fan, to the point he resisted furiously when the producers of Dragonball Evolution tried to make Piccolo look normal and demanded he look like the original character.
He's a comic geek and a gamer to boot.
Throw It In: The scar on his eyebrow is real although it has healed noticeably since Spike's first appearance