An ingratiating comedian and actor with a knack for impersonations and musical parodies, Jimmy Fallon brought boyish energy to the venerable sketch comedy series “Saturday Night Live” (NBC, 1975- ) between 1998 and 2004. His tenure on the show, which included a sublime pairing with head writer Tina Fey on “Weekend Update,” led to several high profile television stints, including host of the MTV Movie Awards in 2005, and appearances in feature films like “Almost Famous” (2000) and “Fever Pitch.” (2005). His movie career never quite panned out, and Fallon kept a low profile until 2008, when he was announced as Conan O’Brien’s replacement as host of “Late Night” (NBC, 1993- ) in 2009.

Born James Thomas Fallon, Jr. in Brooklyn, NY, on Sept. 19, 1974, he was a die-hard “Saturday Night Live” fan from an early age, spending many hours recreating sketches from the show with his sister Gloria as they grew up in Saugerties. A regular performer in high school drama club productions and talent shows, Fallon made his stand-up debut at 17 and left college a semester shy of graduation in 1996 to pursue comedy in Los Angeles. By 1998, he was studying with the legendary improv group the Groundlings and earning his dues as a stand-up comic in local clubs. Trimmed from his first two appearances in feature films, he made his official acting debut in a 1998 episode of “Spin City” (ABC, 1996-2002) just two months before he was summoned to New York to audition for “Saturday Night Live.” His audition, filled with impersonations of Jerry Seinfeld, John Travolta, and former “S.N.L.” breakout star Adam Sandler, won over producer Lorne Michaels, who hired him as a featured performer for the 1998-99 season. That same year, he penned a book of humor titled I Hate This Place: The Pessimist’s Guide to Life with his sister Gloria.

Fallon’s boundless energy, which frequently caused him to break character in the middle of sketches, and knack for characters in the grip of arrested development endeared him to audiences, and he was made a full cast member in the summer of 1999. Among his more memorable roles were Sully, one half of the hormonally charged “Boston Teens” with Rachel Dratch; chemically inspired college student and Internet talk show host Jarret; and unpleasant tech support know-it-all Nick Burns. Fallon also gave note-perfect imitations of celebrities, both notable (Fallon played a younger Mick Jagger opposite the real article in a memorable episode) and otherwise (Carson Daly, Pat O’Brien). But his best showcase came as co-host of “Weekend Update” with Tina Fey, beginning in 2004, where he was frequently given airtime to perform song parodies or deliberately inane song tributes to upcoming holidays. Their chemistry as a team proved exceptionally popular with viewers, and helped elevate Fallon’s standing as a possible breakout performer.

Fallon’s first major appearance away from “S.N.L.” was as host of the MTV Movie Awards in 2001, which was highlighted by his turn as Keanu Reeves’ Neo in an amusing parody of both “The Matrix” (1999) and “Sex and the City” (HBO, 1998-2004). He followed this with a virtually unrecognizable performance as the ironically named Dennis Hope, manager for the ill-fated ‘70s rock band Sweetwater, in Cameron Crowe’s instant classic, “Almost Famous.” Fallon showed some dramatic potential in the film, most notably in its infamous plane-in-a-storm sequence, where Dennis admits to a particularly horrible deed. Fallon also played it straight for a cameo in Steven Spielberg and Tom Hanks World War II miniseries, “Band of Brothers” (HBO, 2001).

Fallon returned to MTV to host the 2002 Video Music Awards, where his talent for impersonating rockers was highlighted in a show-stopping medley featuring his imitations of Avril Lavigne, The White Stripes, Eminem and others. Fallon himself cut an album that same year; an amusing blend of parody songs and stand-up bits, The Bathroom Wall earned a Grammy nomination for Best Comedy Album and even a hit single with “Idiot Boyfriend,” a dead-on spoof of 1970s soul co-written by Blondie’s Debbie Harry and Chris Stein.

Fallon’s movie career appeared to kick into high gear in 2003 with major roles in two features, including the Woody Allen comedy “Anything Else.” Unfortunately, both that film and his other feature that year, “The Entrepreneurs,” were met with dismissal and even outright hostility by audiences and critics. Regardless, Fallon departed from “Saturday Night Live” in 2004 and began work on his next feature, the comedy “Taxi” with Queen Latifah. A remake of a 1998 French comedy by Gerard Pires, the film’s loud, crass humor earned it a quick demise at the box office. Fallon returned to MTV for a third time to host the MTV Movie Awards in 2005 before beginning work on the romantic comedy “Fever Pitch” (2005), which was based on the novel by Nick Hornby. The film, which co-starred and was co-produced by Drew Barrymore, moved the action of the novel from England’s football fields to Boston’s Fenway Park, where diehard Red Sox fan Fallon meets and falls in love with Barrymore against the backdrop of the 2004 World Series race. The finale of the film featured Fallon and Barrymore racing out onto the field at Fenway to celebrate the Red Sox’s first World Series win in 86 years. The film itself, however, was only a modest success at the box office.

Following the mediocre response to his movie efforts, Fallon kept a low profile for the next few years. He lent his voice to two animated efforts, “Doogal” (2006) and “Arthur and the Invisibles” (2007), and played Edie Sedgwick’s promoter Chuck Wein in “Factory Girl” (2006), all of which were met with underwhelming box office numbers. He also kept busy on the comedy club circuit and contributed to the 2006 edition of The Secret Policeman’s Ball, which raised money for Amnesty International. Fallon gained some positive press in 2007 for contributing the proceeds from his humorous song “Car Wash for Peace” to charity, and for giving a note-perfect parody of Internet sensation Lonleygirl15 in a video that made the rounds on the Web.

Fallon’s name returned to the news in 2008 when he was mentioned as a possible replacement for Conan O’Brien after the “Late Night” host assumed the mantle of “The Tonight Show” (NBC, 1954- ) in 2009. He was officially confirmed as O’Brien’s successor in April of 2008, which was followed by a formal announcement in May, much to the surprise of many who had perhaps dismissed Fallon in the past, or who were surprised to see him front and center after a few years spent lying low.