Michelle  Williams dress david letterman legs smile

Michelle Williams made an appearance on The Late Show with David Letterman last night, and the actress is promoting her new flick, OZ The Great And Powerful, where she plays Glinda the Good Witch.

Maybe the long blonde tresses Michelle sports in the film inspired her to grow out her short blonde bob? "I think I'm ready," she told E! News when asked about the process. "It's on its way, slowly but surely."

Williams added that the grow-out period is the main reason she's avoided it. "That's why I've stayed with short hair for so long," she said. "The mid-stage is insufferable. It's really hard on your self-esteem."

"What Matilda would love is for her mom to grow out the cropped hair, though that's unlikely to happen any time soon," Williams told ELLE in late 2011, adding that her late partner Heath Ledger was a huge fan of the 'do. "I cut it for the one straight man who has ever liked short hair and I wear it in memorial of somebody who really loved it."