Robert Dale McElhenney was born, in Philadelphia, PA, and grew up in South Philly with the area's thick urban accent. McElhenney attended the Catholic elementary school Waldron Mercy Academy in Merion Station, and went on to secondary school at the Jesuit-run Saint Joseph's Preparatory School in Philadelphia. It was during his high school years that he attempted his first dramatic work, trying out for a production at the Academy of Notre Dame - an all-girls school - specifically in order to meet girls. After graduating in 1995, he matriculated at the city's Temple University, but dropped out after his first semester and moved to New York City. It was there when he met various service industry denizens living dual lives as thespians, that he began considering taking his own shot at show business. He studied at the Lee Strasberg Theatre and Film Institute and landed his first TV job in 1997 with a guest role on NBC's New York-shot cop procedural drama, "Law & Order" (1990-2010). He managed to land small parts in East Coast film productions, such as "The Devil's Own" (1997) and "Wonder Boys" (2000), though most of his work - including scenes with Brad Pitt and Harrison Ford in the former and Katie Holmes in the latter - wound up on the cutting room floor. He managed a bit more screen-time in Jill Sprecher's indie drama "Thirteen Conversations About the Same Thing" (2001), and a bit less in the New Jersey-shot horror film, "Campfire Stories" (2001), as well as the New York indie comedy, "Long Story Short" (2002). After seven years in Manhattan, he moved to Los Angeles in search of more fertile ground.Once ensconced in Hollywood, McElhenney landed a supporting role in "Latter Days" (2003), playing the leader of a Mormon mission coping with a missionary who shocks his homophobic LDS church by developing a relationship with his openly gay neighbor. He followed that with a sweet turn as Marla Sokoloff's boyfriend in the indie romantic comedy "The Tollbooth" (2004). He won a guest-shot on the long-running NBC drama "ER" (NBC, 1994-2009), but continued to wait tables to pay the rent. In the meantime, he and fellow struggling actors Charlie Day and Glenn Howerton hatched their own concept for a TV show; a would-be chronicle of the foibles of down-and-out and not necessarily likable actors struggling to find work in L.A., which they called "It's Always Sunny on TV." They shot a workmanlike pilot with a camcorder, using their own apartments as sets, and McElhenney's agent shopped it off to TV networks, all of which either passed or returned "notes" that watered down the creativity. But FX - then in the process of rebranding itself as a basic cable repository of edgy original programming - greenlit seven initial episodes of the show. They shifted the premise to McElhenney's native Philadelphia, where they would shoot exteriors, and they made the show on a shoe-string, casting themselves as three of their central foursome, with McElhenney playing Mac, the ever-randy, macho pseudo-reactionary one of the bunch; Howerton as Dennis, the vain, semi-sophisticated but ultimately vapid one; Day as "Charlie," their dimwitted, borderline illiterate janitor and punching bag; with Kaitlin Olson, a veteran of L.A.'s famed Groundlings comedy troupe brought on to play Dennis's sister Dee - all referred to collectively as "The Gang." Premiering in August 2005, the show followed the foursome's shenanigans in and around the bar they ran in South Philly, and, with FX giving them a relative free hand to write the characters and their machinations as depraved as they wanted - one episode saw Mac, attempting to seduce a former school coach into a molesting him after having heard the coach had molested others in his class - all set to chipper string music that hearkened back to lily-white family sitcoms of TV's Golden Age. Though it debuted to mixed reviews and meager ratings, the show developed a frenzied buzz, especially among young adult viewers, and though FX execs initially balked, they renewed "Sunny" for another season when Danny DeVito - whom they had heard was a fan of the show - agreed to join the cast as Dennis and Dee's prodigal (and equally amoral) father, Frank. McElhenney took on show-runner responsibilities, while the three creators continued to write all the episodes, floating such cringe-worthy plot devices as Dennis joining an anti-abortion group just to score with a pro-life girl, and yielding such jaunty titles as "Mac Bangs Dennis' Mom," "The Gang Exploits the Mortgage Crisis" and "Sweet Dee's Dating a Retarded Person." Offscreen, McElhenney and Olson began dating, and, as the show became one of the top draws on FX, it buoyed McElhenney's prospects. One fan of the show, Damon Lindelof, an executive producer of the ABC sci-fi hit series "Lost" (2004-10), threw him a featured guest role in an episode of the series in 2007, which McElhenney would go on to reprise in the show's final season.In 2008, FX picked up "Sunny" for another 52 episodes, assuring its continuation through a 2011 season. In addition, FX's sister network Fox gave McElhenney, Howerton, Day and "Sunny" staffer Adam Stein the greenlight to develop the series, "Boldly Going Nowhere," a riff on the opening credits of various "Star Trek" series that exposes a similarly flawed bunch of characters for whom life on a space ship is less a spectacular adventure than a mundane floating office job. The show was floated as a possible 2009 mid-season replacement show for Fox, but was temporarily shelved. Also in 2008, Olson and McElhenney married. In 2009, the "Sunny" crew took an expanded version of their offbeat musical episode, "The Nightman Cometh," on tour, playing theatrical venues in New York, Boston, Seattle, San Francisco, Los Angeles, and Philadelphia. In 2009, Olson's pregnancy by McElhenney was written into "Sunny" as a mystery seeded in at a drunken Halloween party with the other members of "The Gang" fearing they were the father. The couple had a son in September 2010, with Olson going into labor while they attended a Philadelphia Phillies-L.A. Dodgers game. The cast became major celebrities in Philadelphia, and McElhenney and Olson, in a case of life imitating art, opened their own bar, Mac's Tavern, in the city's Old Towne neighborhood in 2010.