The 33-year-old actress was drawn to new animated movie Monsters vs Aliens in which she voices the character of Susan, a woman who suddenly becomes 49ft tall - because it reminded her of her own struggles to be accepted.
She said: "I really had to learn that it's OK to be who you are, and that you don't have to be cool all the time. I was trying to be cool for so long and it wasn't working. Now I accept that I'm just a big dork, and I'm so much more comfortable in my own skin."
Reese admits one of the reasons she struggled to fit in at school was because she was such a keen student.
She said: "I was a big English kid at school. I loved English class more than anything, and I'd follow my teachers around saying, 'What should I read next?' I was a little obnoxious like that."