(Video Link)

Victor Youk graduated from high school last Saturday. He was disappointed that his school firmly disallowed decorating mortar boards, so he figured out a way to rebel against the policy without getting caught -- at least until the ceremony was over.

Youk placed a tiny ultraviolet infared light in his cap. It blinked, in Morse Code, "Congratulations Class of 2011". The message is invisible to the human eye, but video cameras should pick it up.

Link -via GearFuse