1001 Video GamesThe Arcade version of Ikari Warriors appears in the book 1001 Video Games You Must Play Before You Die by General Editor Tony Mott.
BPjS/BPjM indexOn June 30, 1988, Ikari Warriors was put on the infamous German index by the BPjS. For more information about what this means and to see a list of games sharing the same fate, take a look here: BPjS/BPjM indexed games.
CameosThe Ikari Warriors (Ralf & Clark) would later appear as playable characters in SNK's The King of Fighters game series with brand new looks and moves. Interestingly enough, on the first KOF (where teams are country-based), the Ikari Warriors represent Brazil.
C64 version differencesThere are two completely different C64 conversions of the game. The US version was done by Quicksilver. The European version was done by Elite. The European version has better graphics, sound, and gameplay. It also uses the upper and lower screenborder and doesn't use the whole horizontal resolution to imitate the vertical look of the arcade.
ZX Spectrum versionWondering why the Spectrum version was released so late, especially considering that the ST and Amiga versions were released first? So are many Spectrum enthusiasts. Famed programmer David Perry worked on a version that was due for release in late 1986 - no one knows for sure why this version was scrapped, and a different version not released for another 18 months.
Information also contributed by Martin Smith , nudgegoonies, and Xoleras