(written from a Production point of view)
Keith Carradine (born 8 August 1949; age 71) is the singer and actor who portrayed A.G. Robinson in the Star Trek: Enterprise second season episode "First Flight". Born in San Mateo, California, he is the son of John Carradine (1906–1988), the half-brother of David Carradine (1936–2009) and the brother of Robert Carradine (born 1954).
Keith Carradine gained fame for winning an Academy Award and a Golden Globe for the song "I'm Easy", which he wrote and sang for director Robert Altman's 1975 film Nashville. Carradine even shared a Grammy Award nomination for Album of Best Original Score Written for a Motion Picture or Television Special. Carradine also starred in this film, along with fellow Star Trek performers Robert DoQui, Henry Gibson (who was among those to share the Grammy nomination), and Bert Remsen. However, Carradine actually made his acting debut several years earlier as a cowboy in Altman's McCabe & Mrs. Miller, co-starring fellow Trek actors Rene Auberjonois, Robert Fortier, Bert Remsen, and John Schuck – all of whom were members of Altman's informal acting troupe.
Four years later, Carradine was cast by Altman in the starring role of 1974's Thieves Like Us. Other members of the Altman troupe returning for this film were Bert Remsen and John Schuck, while Louise Fletcher co-starred. Carradine worked alongside Fletcher again in 1996's 2 Days in the Valley, which also starred Teri Hatcher and Lawrence Tierney.
Carradine has many other notable films to his credit. In 1973, he had a supporting role in Robert Aldrich's Emperor of the North Pole, along with fellow Star Trek alumni Hal Baylor, Elisha Cook, Jr., Sid Haig, and Vic Tayback. That same year, he co-starred with Robert Walker in the drama Hex. In 1976, he worked with Sally Kellerman in Welcome to L.A., and the following year, he starred in Ridley Scott's The Duellists, which also featured an appearance by W. Morgan Sheppard. In 1978, Carradine starred in the drama Pretty Baby, co-starring Gerrit Graham.
In 1980, Carradine co-starred with brothers David and Robert in Walter Hill's acclaimed Western The Long Riders. Carradine would star in two more films from Walter Hill: 1981's Southern Comfort and 1995's Wild Bill (the latter featuring Bill Bolender). He also starred in four films from director Alan Rudolph (a protege of Robert Altman): 1984's Choose Me with John Larroquette; 1985's Trouble in Mind with Albert Hall and Bill Smitrovich; 1988's The Moderns with Wallace Shawn and Geneviève Bujold; and 1994's Mrs. Parker and the Vicion Circle, also with Wallace Shawn as well as Matt Malloy and Mina Badie.
Caradine's other films include the 1984 romantic drama Maria's Lovers (co-starring John Savage and Bill Smitrovich), the 1995 thriller The Tie That Binds (with Willie Garson, Barbara Tarbuck, and Ned Vaughn), and the 1997 drama A Thousand Acres (with John Carroll Lynch, Kenneth Tigar, and Bob Gunton). His more recent film credits include 2001's Wooly Boys (with Rosana DeSoto) and 2002's The Angel Doll, a Christmas movie in which he played the adult version of the character played by Michael Welch. In 2007, Carradine starred in the western comedy All Hat, along with Stephen McHattie.
In 2010, Carradine joined the cast of Cowboys & Aliens, a sci-fi/western film scripted and produced by Alex Kurtzman, Roberto Orci, and Damon Lindelof. Fellow Enterprise guest star Clancy Brown also has a role in this film. Carradine wrapped his scenes for Cowboys & Aliens on 14 September 2010. 
Carradine's numerous television roles range from his Emmy Award-nominated performance as Foxy Funderburke in the 1983 mini-series Chiefs (co-starring Stephen Collins and Leon Rippy) to his recurring role as "'Wild Bill' Hickock" on HBO's Deadwood (starring Jim Beaver, Brad Dourif, Paula Malcomson, and Leon Rippy). He has worked on an extensive number of made-for-TV movies and TV pilots, as well. Three TV movies had Carradine acting with fellow Enterprise guest star Fionnula Flanagan: The Godchild (1974, also featuring Ed Bakey, Ed Lauter, and Kermit Murdock), Scorned and Swindled (1984), and A Winner Never Quits (1986).
In 1972, Carradine worked with brother David as well as Keye Luke and Robert Ito in the pilot movie for Kung Fu. That same year, Joseph Sargent directed Carradine in an unsold pilot called Man on a String, which co-starred Byron Morrow, William Schallert, James B. Sikking, and Garry Walberg. In 1986, Carradine starred alongside Saul Rubinek in the HBO film Half a Lifetime, which earned Carradine a CableACE Award nomination. His more recent TV movie credits include Payoff (1991, with Lawrence Monoson and Jeff Corey), In the Best of Families: Marriage, Pride & Madness (1994, with Ken Jenkins), Special Report: Journey to Mars (1996, with Rosalind Chao, Deborah Lacey, and Alfre Woodard), Hard Time: Hostage Hotel (1999, with Elizabeth Dennehy, Roy Jenson, Tony Plana, and Richard Riehle), and Monte Walsh (2003, with Wallace Shawn and Marshall R. Teague).
Carradine also co-starred with F. Murray Abraham, Brad Greenquist, and Jimmie F. Skaggs in the 1996 mini-series Dead Man's Walk, and in the following year, he and Duncan Regehr were regulars on the short-lived series Fast Track. Carradine more recently starred as Nick Savage on the TV sitcom Complete Savages, which lasted one season (2004-05). He also appeared in the acclaimed Steven Spielberg-produced mini-series Into the West, as did Clayton Rohner, Keith Szarabajka, and Star Trek: Voyager''s Garrett Wang.
In 2007 and again in 2009, Carradine played the recurring role of Special Agent Frank Lundy in the second and fourth seasons of the hit Showtime series Dexter. During his time on Dexter, Carradine worked with such performers as Tony Amendola, Jonathan Banks, Adrienne Barbeau, James Ingersoll, Don McManus, and Albie Selznick. Carradine also had a recurring role on the CBS series Numb3rs in 2008. In 2009, he had recurring roles on the Starz network series Crash (working with Linda Park and Julie Warner) and the short-lived Fox series Dollhouse (including an episode directed by Jonathan Frakes). More recently, he played the recurring role of Julian Decker on the FX series Damages, on which he worked with Len Cariou and Wallace Shawn.
Carradine played Wyatt, the father of Penny on The Big Bang Theory episodes "The Boyfriend Complexity" (2010) and "The Bachelor Party Corrosion" (2015).