Joining the ranks of early 2000s teen queens Lindsay Lohan and Hilary Duff, Larson nabbed a record deal, releasing tracks like "She Said" in 2005 at only 16.
In the music video for "She Said," her highest-charting single from first album Finally Out Of P.E., Larson rocked out on a green guitar while donning the fashions of the day: a zebra-print shirt and frayed miniskirt.
Larson even hit the road, joining Teen People's 2005 Rock in Shop mall tour with the likes of Jesse McCartney.
"Today, I would say music is, like, the coolest thing ever, but if I get a feature film tomorrow then acting would be the one," Larson, now 26, adorably told MTV on the set of the "She Said" music video.
Explaining her album's title, she said, "When I found out that I got a record deal, I knew that I was finally gonna be able to be homeschooled, and I was like 'Yes! I'm finally out of P.E.' "
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The Room star made it all the way to N.Y.C., performing during the Macy's Thanksgiving Day Parade in 2005 atop that year's Barbie float.
Larson's early years extended beyond being a T.R.L. hopeful, though. She had small parts in teen flicks including Sleepover and the romantic comedy 13 Going on 30.
Disney Channel fans will also remember the star from original movie Right on Track in 2003.
Larson shifted back into acting in 2006 with a starring role in Hoot, later joining the cast of United States of Tara in 2009 and appearing in 21 Jump Street in 2012.
The rest, of course, is non-musical history.