YouTube is alive with the sound of musicals

• Todrick Hall popped out of the %27Idol%27 pack%2C but he%27s attracted millions with his original videos
• Disney princesses and %27Star Wars%27 proved fodder for brother duo AVbyte
• %27Side Effects%27 takes the trend seriously%2C with a 40-minute musical about bullying and loss

Not many Internet sensations can attribute their career to a No. 6 super-size burger with only mustard and ketchup, large fries and an M&M McFlurry.

But Todrick Hall can. A handheld video of him and his friends singing that order a capella at a McDonald's drive-through instantly became a viral hit in 2010, garnering more than 7 million views to date and launching a successful career for the Season 9 American Idol semifinalist as the face of a burgeoning YouTube trend: musicals.

Gaining a following of more than 600,000 subscribers with flash-mob videos and parody trailers over the past couple of years, Hall is now making elaborate, Broadway-style productions for YouTube, whether it's an eight-minute Cinderella story set to the songs of Beyoncé (titled Cinderoncé, with more than 1.5 million views) or a six-minute retelling of The Wizard of Oz, featuring a mashup of top-40 singles and starring popular a cappella group Pentatonix (The Wizard of Ahhs, 4.8 million views).

"I'm an unconventional artist," says Hall, 28, who is managed by Scooter Braun (the name behind Justin Bieber) and contributed choreography to Beyoncé's Blow video. "When I was on Idol, people wanted to see me be more R&B, urban or hip-hop, but that's not me. ... What YouTube does is allow artists to express themselves freely. Everybody has an equal opportunity to make their careers successful, based on their own ideas and content, and how much effort, money and time they're willing to invest."

Since Hall, countless artists have grabbed that opportunity and found varying degrees of popularity. Brother duo AVbyte has garnered more than 50 million combined views with its videos, which include Hipster Disney Princess and musical spins on Star Wars, Grand Theft Auto V and Facebook. Boy wizard Harry Potter also proves to be ripe for musical material, with Harry Potter in 99 Seconds racking up more than 18 million views to date and the 23-part, Darren Criss-starring A Very Potter Musical totaling nearly 70 million views and inspiring two sequels.

Unlike TV, artists aren't limited by running times and commercial breaks on YouTube, and can freely let their pop-culture and musical sensibilities work hand in hand.

"You think about how many people grow up doing theater but don't necessarily have an outlet for those skills — we're seeing people take advantage of the open platform (of) YouTube to show off their talent," says Kevin Allocca, YouTube's head of culture and trends. Although musicals have been thriving on the site for years now, "what we've seen change is the scale, quality and audience that is consistently there for these videos."

One of the most recent and influential of this new brand of musical is Side Effects, a 40-minute musical that incorporates popular songs from artists such as Taylor Swift, Ke$ha and David Guetta, and follows a 16-year-old girl struggling with high-school bullies and the loss of her parents. It's a bold new step into serious fare for the musical trend, and one that's paid off in more than 2.5 million views since late October for young production company and YouTube channel AwesomenessTV, which creates content geared toward teens.

"To be able to scale an audience like we have so quickly has been amazing, and that's because the funnel of YouTube is so big," says founder Brian Robbins. "I'm just really encouraged by what we've been able to build so quickly. The sky's the limit and YouTube is just the beginning, they're still kind of a baby in diapers. ... A lot of people still look at YouTube as amateur videos, but when the story's really told, these brands will be built on the back of YouTube, comparable to the early days of cable."

The visuals and production quality of Side Effects is "something that hasn't been seen on YouTube," says Robbins, who attributes the video's unique success to its relatable story and authentic, honest characters.

And relatability is a key ingredient to viral success, says Hall, who fondly remembers an elementary school teacher who told him, "If you can make people laugh or cry, then you have them."

"That's true of most videos that go viral," Hall says. "They're either funny or they're so heartwarming and touching, like a proposal or something that someone does for a kid with cancer. Anything that people can relate to is the recipe for a viral video."