A Japanese company which developed arcade games, mostly Shoot Em Ups, from 1984 to 1994.
Most of Toaplan's earlier games were distributed by Taito. Their later shoot-em-ups put more and more bullets on the screen, culminating in Batsugun, the Trope Maker for Bullet Hell shooters.
After Toaplan's demise, many of its employees went to CAVE, Eighting Raizing, Takumi and Gazelle.
Nothing to do with plans hatched by a certain species of robotic heroes.