Possible Clues:

• Unfortunately thrown into a role that didn't suit one?
• As the non-angler given the role of fisherman did and was?
• Scene with amateur in film -- characterising one in unsuitable role?
• The accountants are not given the right part in the fog
• Frenchman is found in the wrong role
• Mechanic initially is thrown, having the wrong part
• Comical chap, not the last in film given unsuitable role
• Given an inappropriate role
• In the wrong acting role
• Put in the wrong role