All Six Degrees:
Natalie Garza (The List, 2006) Malcolm-Jamal Warner (Restaurant, 1998) Adrien Brody (The Pianist, 2002) Maureen Lipman (Educating Rita, 1983) Michael Williams (Marat / Sade, 1967) Patrick Magee (A Clockwork Orange, 1971) David Prowse - Darth Vader (body)
... and the quickest I could find:
Natalie Garza (The List, 2006) Brad Dourif (Grim Prairie Tales, 1990) James Earl Jones - Darth Vader (voice)
... making up the whole of Darth Vader!!
Happy Birthday, Tim Robbins!