That was the question Aki Saito asked in a Metal Gear Integral podcast. For those who don't know Zone of the Enders (ZoE), it is a high speed action mecha action game. ZoE spawned two three sequels as well as two anime. The first title was released on the PlayStation 2 in 2001 with a Game Boy Advance version, Zone of the Enders: The First of Mars, following later that year. A proper sequel, Zone of the Enders: The 2nd Runner, came out in 2003.