The Game: In one of the most seminal variations on the Space Invaders format, Galaxian was among the first clones to introduce attacking formations that would break off from the usual rows and columns of 
invaders. Though Galaxian‘s use of this innovation was minimal, it was a drastic change from the usual slowly-advancing target gallery. (Bally/Midway [under license from Namco], 1979)
Memories: Galaxian may not be as well remembered as the much more strategically challenging Galaga, but it ultimately added a vital new twist to the Space Invaders-inspired genre, a format which was badly in danger of becoming stale. Galaxian was also the first arcade video game to use a color display instead of a monochrome monitor with translucent colored overlays.
The mothership from Galaxian appeared in some later levels of Pac-Man as a substitute for the cherries, apples, and other fruits which would periodically appear as bonus items at the center of the maze. Galaxian‘s mothership also appeared as a bonus item in one of the final entries in the Pac-Man franchise, Pac ‘n’ Pal. Galaxians also appear in Galaga and Gorf.
Galaxian was a relatively simple game to adapt for home play, but it didn’t arrive in Atari 2600 form for several years. For quite a while, the only home version of Galaxian was Coleco’s tabletop arcade game, which was a rather faithful rendition, right down to the arcade cabinet art, which looks like it fell off of a Yes album somewhere.