My nephew tried that once years ago....he came at us through the back doorwall wearing a gorilla mask. He wasn't trying to antagonize the dog (we had a female GSD at the time, she was just about a year old), just trying to scare us...we got the last laugh when the GSD chased him back out the door and across the yard, her barking and him yelling and all the while wearing the gorilla mask. Sigh...where are the video cameras when you need 'em?