(written from a Production point of view)
James H. McGrath, Jr. is the father-in-law of Star Trek and Star Trek Into Darkness director J.J. Abrams; his daughter, Katie McGrath, has been married to Abrams since 1996. The elder McGrath appeared in Star Trek as a barfly, along with Abrams' own father, Gerald W. Abrams. McGrath and Abrams also appeared in the sequel Star Trek Into Darkness as Starfleet admirals at the memorial service.
McGrath, Jr. also had a featured part as an old man on the piano in the 2003 crime thriller Owning Mahowny.