Shortly before his recent passing, Marlon Brando voiced Mrs. Sour (see image at right) in BIG BUG MAN - an absolutely awful-looking hand drawn animated film about a candy factory worker (Brendan Fraser) who gets superpowers after insects bite him, set for release in 2006. Apparently Brando did it wearing a blond wig and a dress, with full makeup and white gloves, according to writer/co-director Bob Bendetson. "I guess it was part of his Method training or something," Bendetson said.
See a CNN report on this film here (Quicktime required) or read more about it here.