She rocked stick-straight blonde hair for 2004's "Mean Girls," because nothing says "I'm a mean girl" more than long blonde hair and a pink mini skirt.
McAdams' character Allie and her perfectly put-together hair stole our hearts in 2004's "The Notebook."
The actress showed up to the June 2004 premiere for "The Notebook" incognito with bangs, a choppy bob, and chocolate brown hair color.
McAdams wore her hair red with a slight wave for the MTV Movie Awards in June 2005. Perhaps she knew she was going to win "best kiss" for "The Notebook" and wanted to get the look from the movie back?
Rachel arrived at the July 2005 premiere for "The Wedding Crashers" with her hair blonde and pulled back with a headband. We can't get over how much she resembles Barbara Eden from "I Dream of Jeannie" in this one. That's five different hair colors in a year so far, if anyone is counting.