We think this bob was the real thing at "The Time Traveler's Wife" premiere in August 2009, but you never can tell with the Hollywood set.

Just four months later, McAdams debuted this long braided look at the premiere of "Sherlock Holmes" in the UK. Either she's got the hair-growing power of Superman, or this braid is an extension.

Is anyone else having "Friends" flashbacks? Rachel sported, uh, Rachel at the NYC premiere of "Morning Glory" in November 2010.

McAdams' locks looked slightly brighter at the Cannes Film Festival in May 2011.

McAdams kept her blonde hair simple and wavy at the Cannes premiere of "Midnight in Paris" in May 2011, because the real star of this show was her red Marchesa dress.