Heidi Montag Cast in Movie With Jen Aniston!

Credit: Chris Weeks/WireImage.com; Jon Furniss/WireImage.com

Heidi Montag: movie star?

"I was just cast in my first feature film comedy!" the reality star, singer and plastic surgery fan Tweeted late Wednesday. "I start filming monday!!!!!

The 23-year-old couldn't contain her excitement: "this is one of the best days of my life!!! getting ice cream to celebrate!...jump for joy!"

And it's not a B-movie directed by her husband Spencer Pratt, either. It was later confirmed that Montage will cameo in Just Go With It, a 2011 romantic comedy starring Adam Sandler, Jennifer Aniston and Nicole Kidman.

The Hills star isn't the only newbie: Sports Illustrated model Brooklyn Decker (wife to Andy Roddick) will also appear in the film, which was previously titled The Pretend Wife.

"It's a new day, a new beginning...memorizing my script for the feature comedy movie I am filming all next week," Montag added Thursday.

Here's hoping that Montag's movie debut goes more smoothly than her foray into music: her album Superficial sold less than 1000 copies in its first week back in January.