The term "giant enemy crab" was coined by Game Republic's producer Bill Ritch during the Sony 2006 E3 Press conference while demoing Genji: Days of the Blade. Ritch explained that the game featured "real time weapon change" and that it was based on "famous battles which actually took place in Ancient Japan", suggesting that the battles within Genji 2 had some historical credibility. Later in the demo however, Ritch came across a "giant enemy crab." there is a growing consensus among historians that giant enemy crab attacks were quite rare, at least in ancient Japan. Because of the absurdity of the presentation, the phrase was often used to showcase the ridiculous nature of the demo. "Giant Enemy Crab" was later used in many other games as a reference to the infamous moment.
Outside of the legendary crabs in Genji, many other games have featured giant enemy crabs. To explain behemoth crabs, magic, radioactivity, and other methods are usually to blame. Sometimes, the crabs are just huge. Vagrant Story, Metal Slug, and other games all featured giant enemy crabs, none as popular as the historically accurate crabs featured in Genji.
Six months after the infamous Sony 2006 E3 Press conference, Rare's first installment of it's new franchise, Viva Pinata, contained a reference to Bill Ritch's speech. A loading screen in the game, which normally give you helpful gameplay hints, instead stated that the game contained "real time tool change" and that the player could "wallop Seedos' weak point for massive seedage", much like the Giant Enemy Crab in Genji: Days of the Blade.
The game Scribblenauts includes the word "giant enemy crab", as well as a level that gives you the hint "for massive damage!". Roaming around the level are 3 samurai, a reference to the character designs in Genji II. In addition, to defeat the crab, it is easier for it to be flipped over, attacking the weak point on the bottom for massive damage.