{alltv} Two of a kind: Justin Bieber and Susan Boyle

YouTube sensations Justin Bieber and Susan Boyle have racked up a fleet of die-hard fans in just a few years. The adorable Canadian sensation started out small and is now a Twitter-driven pop superstar with backing from Usher and Justin Timberlake. Boyle's shocking Britain's Got Talent performance has skyrocketed her to chart-topping records and worldwide recognition.

A timeline of their success:

2007: Justin Bieber, a 12-year-old Ontario native, enters a local singing competition called Stratford Idol and comes in second place. With his mom's help, he starts posting YouTube videos of himself singing in his bedroom, which go viral.

2008: Former So So Def marketing executive Scooter Braun discovers Bieber on YouTube and flies him out to Atlanta, where the teen impresses R&B star Usher, who signs him to Island Records.

April 11, 2009: Scottish hopeful Susan Boyle appears on Britain's Got Talent, singing I Dreamed a Dream from Les Miserables. The show is seen by more than 10 million viewers; a clip of Boyle's performance gets 2.5 million YouTube hits within the first 72 hours.

May 30, 2009: Although a fan favorite, Boyle loses the competition, placing second to the dance troupe Diversity. She is treated for exhaustion in London after the finale.

Nov. 17, 2009: Translating his skills from YouTube to the recording studio, Bieber releases his debut album My World, a pop-R&B album that goes platinum. His is the best opening release for a new artist in 2009 until Boyle tops him later in the year.

Nov. 20, 2009: A scheduled Bieber performance at Roosevelt Field Mall on Long Island is canceled because of a massive, out-of-control crowd.

Nov. 23, 2009: I Dreamed a Dream, Boyle's first album, sells 9 million copies worldwide. The record has the year's biggest first-week sales in the USA (edging out Eminem's Relapse) and receives more advance orders than any recording in Amazon.com history.

December 2009: The TV special I Dreamed a Dream: The Susan Boyle Story (Dec. 13) documents her success and features a duet with Boyle's idol Elaine Paige. She's voted the seventh most influential person in the world by Time magazine and runs the guest-appearance gambit (including interviews with Larry King and Oprah Winfrey) and is spoofed on shows like 30 Rock and Saturday Night Live.

Dec. 20, 2009: Bieber performs for the Obamas and has high-profile performances and interviews on Saturday Night Live, Ellen and The View.

March 19, 2010: Bieber releases My World 2.0 to deafening Internet buzz. He tears up the charts with singles like Baby, Somebody to Love, and Eenie Meenie.

May 5, 2010: After admitting his celebrity crush, Bieber tweets a photo of him with Kim Kardashian with the caption "look it's my girlfriend." Massive outcry from his Internet following ensues, and Kardashian receives death threats.

Sept. 19, 2010: Boyle is recognized by the Guinness Book of World Records as having the fastest-selling debut album by a female artist in the U.K., most successful first-week sales of a debut album by a female artist in the U.K., and for being the oldest person to reach No. 1 with a debut album in the U.K.

Sept. 23, 2010: Following in the footsteps of Taylor Swift, Bieber makes his acting debut as a guest star on CBS' CSI.

Oct. 12, 2010: Boyle's The Woman I Was Born to Be: My Story (Atria, $26) and Bieber's First Step 2 Forever: My Story (HarperCollins, $21.99) go on sale.

Nov. 9, 2010: For her second album, Boyle will release a Christmas-themed album, The Gift. She hosts a YouTube competition, "Susan's Search," where thousands of fans audition to sing with her on the album. New York resident Amber Stassi wins and records with Boyle in London.

Holidays 2010: "Belibers" can buy collectible dolls, among other branded memorabilia. A Bieber nail polish collection, One Less Lonely Girl, will be coming to Walmart as part of Nicole by OPI.

February 2011: Anticipated release of a 3-D Bieber biopic, directed by Jon Chu (Step Up 3D).