And it turned out to be a shrewd move - one week later she landed her first serious acting role.
When she first started out in the industry, Emma - who's recently scored the role of Spider-Man's new bit of stuff - was limited to playing dumb airheads.
But it all changed for the Superbad star after a trip to the hair salon.
She recalled: "When I first moved to LA, I had this agent who thought, because I was blonde, that I only wanted to play cheerleaders. So she'd send me out for all these parts where they thought: 'What a weird 15-year-old. It's not going to work out!'
"I don't know if anyone necessarily underestimated me as a blonde - I think I just had a crappy agent.
"So one day, in a fit of trying to do something different, I just dyed my hair dark brown and got my first role a week later, after which I thought: 'People are close-minded, man! Like a different hair colour changes everything!'"
Source: thesun
