From the "Special Features" menu, highlight "Filmographies" and press right. The picture of Jack Black will now change to that of him in the chicken suit. Hit enter to view some outtakes of Black in the suit.
When you're returned to the "Special Features" menu, repeat the same process as above, so that the chicken appears on the screen again. After doing so, hit right again; Steve Zahn's picture will now change to that of him with a raccoon on his head. Hit enter to view some behind-the-scenes antics with raccoons both real and fake.