Procedural invaders are space invader like characters generated as 5 x 5 pixel characters from just 15 bits using symmetry. The earliest post on procedural invaders appears to be from a J Tarbell in 2003. Thanks go to Ross McKinlay for suggesting having a look.
Below are some sheets of randomly generated invaders with generated names that you can click on to generate a tweet with F# code that generates the invader as ASCII art when sent to Mathias Brandewinder’s @fsibot.
The sheets of invaders are drawn on to a bitmap image and saved as a png file (see invader bitmap generation F# snippet), with the bit pattern for each invader generated from the hash code of it’s generated name (see pseudoword generation F# snippet). At the same time a matching HTML image-map is generated with the coordinates of each invader with a link that generates a tweet for the specified name.