From the Starting Menu click on Special Features. Notice: This screen has a dead Rhino body, click on Continue at the bottom of the screen. Notice: The screen changes to a police outline of the dead Rhino. From Main Menu at the bottom of the screen, press up to highlight the dead Rhino outline. It changes from Yellowish to Reddish, very faint to see. And press Enter to see an outtake of Robin Williams and Edward Norton introducing the character of Booby McPenis aka "The man who makes the little holes in donuts".
All easter eggs were generously submitted by SirDonk