For those thinking this is a reference to Portal (those people who thumbs down), how could it be a reference? This cartoon came way before the game. This was meant to be a funny video, not a serious video. Think of it as like a very short YouTube Poop without obnoxious noises.
Original Ed, Edd n Eddy clip (One + One = Ed) copyright Danny Antonucci, A.K.A. Cartoon, and Cartoon Network."