* NoExportForYou: The 3D installment for {{Playstation 2}} has not been released in North America.
** Also, from the main series, the Combat School, a mission-based DatingSim.
* PortOverdosed: SNK just loooooooooves re-releasing the original game. It's hard to find a single compilation by them that doesn't include it.
* WhatCouldHaveBeen: Early on, Sophia was considered to play the role of Player 2.
** Many ideas and models were scrapped from the final product, expecially in 5. Including a giant turtle-like mecha and the native zapped by the lightning at the beginning as the final boss on a levitating, laser-spitting pillar. See [[http://randomhoohaas.flyingomelette.com/MetalSlug-MissingInAction/MSAction-Main.htm this page]] for all the stuff that people have found from the game files.