Trivia
Scott Johnston rendered the Walker (with a 3D program) to get all the different angles right, and then touched it up with a pixel drawing program.
Until a couple of months before its release, the game was to feature 2 different types of levels, alternate levels being platform shooters. However, they decided that this section wasn't up to standard, and decided to stick to the basic shoot 'em up.
Game was ultimately in development for 3 or 4 years. The Walker project went into limbo for a year or two, during which time someone in DMA Design came up with the idea for Lemmings. Finally, Walker was released in 1993.