WATCH: 'The Hangover Part II' Star Crystal the Capuchin Monkey Crashes the ET Set!

Crystal, the scene-stealing star from 'The Hangover Part II,' gave Nancy O'Dell, Mark Steines and the crew a surprise visit when she arrived at the ET stage!

The 17-year-old Capuchin, who's been in over two dozen films, was all over the place as she spent time in the voiceover booth, helped direct the two hosts and even took to the stage to play co-anchor.

Watch as Crystal steals the spotlight during the taping of ET!