What's the Big Frigin' Difference?!

Can you find the stealthy differences hidden within these photos? Are you good enough to spot 'em?**HINT -- There are THREE differences in the above photographs!**

TMZ
What's the Big Frigin' Difference?!

Source: http://www.tmz.com/2012/01/07/whats-the-big-frigin-difference-photoshop-celebrity-hunt-tmz-games-changes-mixed-up/

Michelle Trachtenberg Jennifer Morrison Jennifer Aniston