Born Peter C. MacNicol in Dallas, TX, he was the son of parents Barbara and John, an Episcopal priest. Raised in the Texas metropolis, MacNicol first attended the University of Dallas, and then the University of Minnesota, during which time he performed for two seasons with Minneapolis' renowned Guthrie Theater. After making the move to the East Coast, MacNicol made his Broadway debut in a well-regarded production of Beth Henley's "Crimes of the Heart" in 1981, and went on to perform frequently at Joseph Papp's New York Shakespeare Festival several times in the years that followed. He made his feature film debut in the fantasy adventure "Dragonslayer" (1981), opposite the esteemed English actor Sir Ralph Richardson, no less. In the special effects-laden extravaganza, MacNicol played Galen, a young apprentice to a wise old wizard (Richardson), tasked with destroying a 400-year-old dragon. Although the movie was not a major box office success, it eventually went on to achieve cult status with fantasy film fans. It also garnered MacNicol notice for his vulnerable performance as the meek, but determined Galen.MacNicol's sophomore effort found him cast alongside Meryl Streep and Kevin Kline in a film considered by many to be the very best of that year - "Sophie's Choice" (1982). Directed by Alan J. Pakula, the film essayed the tragic love story of a guilt-ridden Holocaust survivor (Streep) and her emotionally disturbed lover (Kline), sharing an apartment with an aspiring novelist (MacNicol) in 1940s New York. "Sophie's Choice" went on to win Streep an Academy Award for Best Actress, and officially placed MacNicol on the list of young actors to watch. Over the next four years, the actor confined himself primarily to the stage before segueing to television with the superior production of "Johnny Bull" (ABC, 1986), a drama about a naïve English girl (Suzanna Hamilton) facing some harsh realities after relocating to a rural Pennsylvania mining town with her new husband (MacNicol). Developed at the National Playwrights Conference of the Eugene O'Neill Theater Company, the TV movie afforded the younger actor an opportunity to work with veteran pros Jason Robards and Colleen Dewhurst, as well as relative newcomer Kathy Bates. The following year, he provided much needed comic relief and heart to the action thriller "Heat" (1987), starring Burt Reynolds as a Vegas bodyguard looking to put his violent past behind him.While "Heat" played on cinema screens, MacNicol maintained his stage presence with a 1987 production of "All the King's Men" at the Dallas Theatre Center in his Texas hometown. On theater screens he played a hardworking leader of a 1950s jazz quintet in the little-seen gem "American Blue Note" (1989), in addition to a hilariously demented turn as the thickly-accented museum curator possessed by evil spirits, Dr. Janosz Poha, in the sequel to the hit supernatural comedy "Ghostbusters II" (1989). Other supporting roles at the time included a pair of romantic comedies - "Hard Promises" (1991) and "HouseSitter" (1992). MacNicol took on his first stint as a TV regular on Norman Lear's short-lived political satire "The Powers That Be" (NBC, 1992-93), playing Bradley Grist, the obsequious aide to a clueless U.S. Senator (John Forsythe). Although the show came and went with little notice, MacNicol bounced back with several supporting roles in films that included the successful comedy sequel "Addams Family Values" (1993) and the nostalgic comedy/mystery "Radioland Murders" (1994). Back on television, he temporarily joined the cast of "Chicago Hope" (CBS, 1994-2000) for its first two seasons as Alan Birch, the kind-hearted hospital legal counsel whose sudden, violent death stunned and saddened audiences.In decidedly more light-hearted fare, MacNicol did the best with what he could as Renfield in Mel Brooks' anemic spoofing of the vampire sub-genre, "Dracula: Dead and Loving It" (1995). On television, MacNicol eventually hit weekly series paydirt when he took on the role of quirky law firm boss John 'the Biscuit' Cage on the hit courtroom comedy "Ally McBeal" (FOX, 1997-2002), created and written by "Chicago Hope" mastermind David E. Kelley. The eccentric lawyer - plagued by innumerable nervous tics and phobias - was a perfect fit for the performer's comedic gifts, earning MacNicol successive Emmy nominations in 1999 and 2000, with a well-deserved win in 2001. A creatively satisfying time for the actor, he was also given the opportunity to direct several episodes of the series. Apart from his series, MacNicol played another museum curator who is exasperated by his oddball houseguest (Rowan Atkinson) in "Bean" (1997), a comedy based on a beloved British TV series, which suffered greatly in its cross-Atlantic adaptation. He also played the lead in the adaptation of Southern novelist Eudora Welty's mystery melodrama "The Ponder Heart" (PBS, 2001), as an eccentric man of wealth suspected in the disappearance of his teenage bride (Angela Bettis). Fresh off his "Ally McBeal" run, MacNicol co-starred with Valerie Bertinelli in the made-for-TV adoption drama "Crazy Love" (CBS, 2003), prior to taking on a regular role as Dr. Larry Fleinhardt on the criminology procedural drama "Numb3rs" (CBS, 2005-2010). A brilliant theoretical physicist, Fleinhardt assisted mathematical genius Charlie Eppes (David Krumholtz) and his brother, FBI Agent Don Eppes (Rob Morrow), in solving the most enigmatic of crimes. In a similar vein, MacNicol joined Keifer Sutherland for the 2007 season of the action drama "24" (Fox, 2001-2010) as the ethically-challenged White House Chief of Staff Tom Lennox. For years, MacNicol had been voicing characters for various animated shows and features, a sideline of work he continued with great success on the superhero series "The Spectacular Spider-Man" (The CW, 2008-09) as Doctor Octopus, Peter Parker's multi-armed nemesis. Another recurring role included that of pediatrician Dr. Robert Stark on the hit medical drama "Grey's Anatomy" (ABC, 2005-) in 2010.