For some real excitement, look at how the Apple 2's graphics worked. If you ever worked with hi-res mode you know how screwey the colors were. Turns out they basically serialized the bits right out of ram into a crude NTSC signal and the bits ended up making different frequencies--hence different colors (the high bit of each byte specified whether to delay the rest of the 7 bits by half a clock).

Looking at an Apple 2 schematic is eye-opening. There's hardly anything there!