(written from a Production point of view)
Paul McGillion (born 5 January 1969; age 51) is an actor who appears as the Starfleet Academy barracks leader in Star Trek. He is best known as part of another science fiction franchise, having acquired fandom for his role as Dr. Carson Beckett in the Sci-Fi Channel series Stargate: Atlantis.
Born in Paisley, Scotland, the sixth of seven children, McGillion and his family moved to Canada when he was two years old. He received a Bachelor of Education Degree in Master Scene Study from Canada's Memorial University of Newfoundland, as well as a Bachelor of Fine Arts Degree in Voice from Brock University in Ontario. McGillion himself was an instructor in scene study at the Vancouver Film School in 1998 and 1999.
McGillion has been performing in Canadian theater since 1990. Some of his stage credits include leading roles in Piano, Savage in Limbo, The Foreigner, El Salvador, and Reservations for Two, the latter of which he produced and directed.
He made his television debut in a 1994 episode of ABC's The Commish with Bruce McGill. He later made guest appearances on several science fiction shows, including Sliders (starring John Rhys-Davies), The X-Files (including an episode directed by Cliff Bole), First Wave (with Rob LaBelle), Seven Days (with Vaughn Armstrong, Norman Lloyd, Brian Markinson, and Holmes Osborne), Smallville (with John Glover), and UPN's The Twilight Zone (in an episode with Bill Mumy and directed by Allan Kroeker). He even appeared an early episode of Stargate SG-1, nearly seven years before joining the cast of Stargate: Atlantis.
McGillion's first film was 1995's Crying Freeman, in which he played a detective. Some of his later film credits include Saving Grace (1998), Something More (1999), My 5 Wives (2000), Replicant (2001), and A Guy Thing (2003). He also starred in and produced the award-winning 2003 independent drama See Grace Fly, which earned him two nominations from the Leo Awards.
His early TV movie credits include She Woke Up Pregnant (1996; directed by James Contner), NightScream (1997, with Teri Garr and Ned Vaughn), and Love and Treason (2001, with Timothy Carhart). In 2003, he was seen in National Lampoon's Thanksgiving Family Reunion, along with Hallie Todd. In 2004, he was among the several Star Trek alumni to appear in the TV movie NTSB: The Crash of Flight 323. His co-stars on this production included Roger Cross, Brett Cullen, Richard Riehle, and Freda Foh Shen. McGillion worked with his Star Trek co-star Anton Yelchin in the 2004 TV movie Jack. Also starring in this movie were TNG actors Erich Anderson and Brent Spiner. Another TV movie McGillion appeared in that same year was The Life, which starred fellow Star Trek (2009) cast member Bruce Greenwood.
McGillion made his debut as Dr. Carson Beckett in the pilot episode of Stargate: Atlantis in July 2004. Originally intended to be a recurring role, Beckett became a regular until he was written out of the show in the third season's 17th episode, "Sunday", which aired in January 2007. However, outcry from fans of McGillion and Carson persuaded the show's producers to bring the character back, although not as a regular. He returned in a two-episode arc during the show's fourth season, which premiered in September 2007. He then appeared in five episodes of the show's fifth and final season, which premiered in the fall of 2009. His last appearance was in the series finale, "Enemy at the Gate", which aired in January 2009.
During his years on Atlantis, McGillion worked on several other projects. He had a role in the crime drama The Deal, starring Christian Slater. McGillion then acted with many of his Atlantis co-stars (as well as Stargate SG-1 regular Christopher Judge) in the 2007 comedy film A Dog's Breakfast. In 2008, McGillion portrayed the male lead in the Lifetime TV movie Mom, Dad and Her.
In 2008, McGillion filmed a guest appearance on the FOX Network series 24 for the penultimate episode of the its seventh season, set to air in May 2009. Bob Gunton, Jeffrey Nordling, and Annie Wersching were regulars on the series during that season, and several other Star Trek veterans filmed one-time or recurring appearances, including John Billingsley, Glenn Morshower, Kurtwood Smith, Tony Todd, and Connor Trinneer.
McGillion actually auditioned for the role of Montgomery Scott for the new Star Trek. His audition was held in Los Angeles, having already been suggested as a possible contender for the role of Scotty in fan discussions.
His fans lobbied for him to be cast as Scotty, and also showing support for his casting was Christopher Doohan, the son of James Doohan, the actor who originated the role of Scotty on I AM ERROR. "I think Paul McGillion is a GREAT choice for the role of Scotty," Doohan says. "He has a great accent and I think that he actually looks like my father." Of his potential casting, McGillion says "it would be a great honour to follow in James Doohan's footsteps." 
Ultimately, however, the role went to English actor, comedian and writer Simon Pegg of Spaced and Shaun of the Dead fame. Nonetheless, McGillion still managed to make an impression and was cast in a small role as a Starfleet Barracks officer for a scene opposite Chris Pine as James T. Kirk. McGillion filmed his scenes in November of 2007, the first month of shooting.