Oh, baby!

Kate Middleton may be a style icon now, but before she married into the royal family in April 2011, the phrase "dressing up" had a very different meaning.

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In 2001, Prince William's future wife donned an adult baby costume for an event at St. Andrews University, where she and her husband first met and fell in love.

The Daily Mail reports that the Duchess mentioned the getup last week to a guest at a fundraising dinner at the school.

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"I think there is a photo of it out there somewhere," she told her fellow party-goer of the funny guise.

She was right. The photo, which surfaced soon after the Nov. 8 event, shows a smiling Middleton in full baby-mode, complete with a bib, makeshift diaper, pigtails, and rosy cheeks.

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The good-natured Duchess donned the costume as part of Raisin Weekend, a longtime St. Andrews tradition in which new students are "adopted" by older students (their "academic parents") and welcomed into the school's fold. The festivities typically include a tea party, drinking games, and -- most notably -- a massive foam fight.

This article originally appeared on Usmagazine.com: PICTURE: See Kate Middleton Dressed as "Adult Baby" at College Bash