When you walk up behind an unsuspecting person and go on your toes, stiffen your back, and flap your arms to a 30 degree angle. If you do this after you jump in the air, it's called Flying, Angry Peguining. Like planking but you need another person to do it to.
I was walking in the mall and this guy was Angry Penguining this store clerk. Man it was so funny, he never knew what was going on behind him!