Opening riff 

I'm not a musician so I hesitate to edit the article itself, but... I've been playing "Rebel Rebel" and Zappa's "Trouble Every Day" side by side, and to my ear they open with the exact same guitar riff. Not to mention: same tempo, key, everything. And Trouble Every Day was written in 1965 and released in 1966, years before Rebel Rebel. I guess it could be a coincidence but that seems unlikely. Maybe Bowie heard the Zappa song on the radio & forgot about it, thought he had made it up...