From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
Dean Stockwell (born March 5, 1936 in Hollywood, California) is an American actor. He is best known for his portrayal of "Al Calavicci" in the TV series Quantum Leap, which starred Scott Bakula. In the Re-imagined Series, he plays Number One aka Brother Cavil, a disgruntled, cynical Colonial priest who is later revealed to be a Cylon.
Stockwell is a former child actor whose career included roles with such actors Errol Flynn, Gregory Peck, and Orson Welles. Stockwell was nominated for an Academy Award for his supporting role as Tony "The Tiger" Russo in the 1988 comedy film Married to the Mob.
He also had supporting roles in two David Lynch films: the 1984 adaptation of Frank Herbert's Dune and Blue Velvet. His other film credits include Beverly Hills Cop II, Tucker: The Man and His Dream, The Player, Air Force One and 2004's The Manchurian Candidate.
He made a guest appearance as Colonel Grat on Star Trek: Enterprise during its first season episode "Detained", reuniting him with Scott Bakula, who also had the starring role in that series. Stockwell has also guest-starred on Stargate SG-1.