He will wear a fibreglass head throughout his new film 'Frank'.
Not since John Hurt played the ' Elephant Man' has a leading man been so disguised for a film role.
However, producer Ed Guiney said the false head has not inhibited the Killarney man, working with his fellow cast.
"Michael is Michael after all, even with a fibreglass head on. He keeps the head on for all the scenes in the film. Everyone's just got used to it," Ed Guiney told the Irish Independent from location in New Mexico, where filming started last Friday.
A fictional tale inspired by left-field music figures, including Manchester comedian Frank Sidebottom, who wore a papier-mache head, the film stars Fassbender as the leader of an avant-garde band.
Directed by 'What Richard Did' director Lenny Abrahamson, shooting on the €5m feature moves to Ireland next month in a plot where the group record an album at a remote studio.
Locations include Wicklow and Dublin.