Which filmmaker makes a cameo appearance as 'Senator #2' in the Godfather Part II"?

Among the actors depicting U.S. Senators in the hearing committee in the "Godfather Part II" are film producer/director Roger Corman, writer/producer William Bowers, producer Phil Feldman, and science-fiction writer Richard Matheson. Corman is directly depicted as 'Senator #2'.

In the film in Washington, D.C., a Senate committee on organized crime is investigating the Corleone family. Having survived the earlier attempt on his life, Frank Pentangeli (Michael V. Gazzo) agrees to testify against Michael Corleone (Al Pacino), who he believes double-crossed him. Frank has been placed in the witness protection program to gain his cooperation and testimony.

Within the entire film, the Corleone family roots are explored. It traces Don Vito's journey from Sicily to a life of organized crime in New York, NY. In a parallel story, Vito's grown son Michael extends the family operations to Cuba while dealing with more family betrayal and murder. This movie is excellent on how it covers Michael Corleone's reign as the 'Godfather'.