I actually developed a game which used this trick for an Easter egg. I added in a texture for the Companion Cube from Portal, and set the alpha to 1. In game, h

I actually developed a game which used this trick for an Easter egg. I added in a texture for the Companion Cube from Portal, and set the alpha to 1. In game, however, I loaded the textures with only a single bit of alpha, which meant that the alpha of 1 was the same as 255. Not entirely invisible, but was fun to do!