Development docs for the original Space Invaders, released in 1978 in Japan (design by Tomohiro Nishikado for Taito)
A friend sent me these pictures he took and I thought that would be interesting to share with you. By the way, take a look at this detail from the first one: the most iconical invader represents a space crab. Did you know that?!
Click on the image for a better size.