Trick or treat?!

Mary-Kate and Ashley Olsen got into the Halloween spirit, donning Batman and Catwoman masks while shooting a fun new video for their fashion website, StyleMint.

The 25-year-old twins also dressed up at Stars Wars characters Darth Vader and a Stormtrooper. See more  pics at

StyleMint, which was launched this past spring, is a membership-based site featuring the Olsen's super-soft tees ($29.99 each). Sign up for free, then get monthly e-mails with new styles for you based on an interactive personality quiz.