Fergie is as nice as she is naughty!

Appearing on The Ellen DeGeneres Show Dec. 10, the 37-year-old singer explained how she makes the holidays extra special for Josh Duhamel**, her husband of nearly four years. "One day every holiday season, he comes home and there's a naughty Mrs. Claus," Fergie revealed. "It depends how good he's being!"

The costumes differ "every year," the musician added. "It's a surprise. It's naughty and nice at the same time. It's super cute and fun."

Host Ellen DeGeneres** gifted Duhamel, 40, with a Santa-inspired thong in Dec. 2011, but he's yet to wear it around the house. "It was too small," Fergie explained.

Joked DeGeneres, "That's more information than we needed!"

Fergie also explained why she hasn't mailed out her holiday cards -- typically featuring the famous pair -- this season. (The celebrity couple has also shared them with fans via Twitter and Facebook in the past.)

"My husband orchestrates the whole thing and we're late this year because he's been filming a movie. He just finished Safe Haven with Julianne Hough** and now he's doing You're Not You with Hilary Swank**," the Black Eyed Peas singer said. "I haven't been on the ball, so I'm waiting for him and we're going to have to do something last minute this year."

This article originally appeared on Usmagazine.com: Fergie Wears "Naughty Mrs. Claus" Costume Every Year for Josh Duhamel