The term "Pinwheel Forest" is something of a mistranslation, for the forest's name does not, as outsiders often believe, refer to the small wheels blown by the wind centered by pins that are occasionally placed within the forest for ornamental purposes. In truth, Pinwheel Forest was named for the large, wheel-shaped pokemon who constantly roll around its floor and up its trees, their bodies covered in spikes which the forest's imaginative discoverer once likened to safety pins. Although many pokemon live within its environs, the forest's name is better understood as meaning "Whirlipede Forest" - and centuries later, this name remains an apt one.
This is not because Whirlipede are the most numerous pokemon in the forest – in fact, many trainers find it difficult to make the few they do find stay still long enough to capture them – but because they far and away draw the most attention. Part of this attention is a matter of safety, for Whirlipede are among the most dangerous of the area's pokemon. Smaller obstacles, including many young pokemon trainers, are more often flattened than avoided at the high speeds at which the Whirlipede roll, and even larger objects which could injure them can be difficult for these pokemon to avoid.
Whirlipede rely on this unusual method of locomotion for survival, as rolling allows them to escape predators and chase down even arboreal prey. But with the growing number of human visitors, Pinwheel Forest's Whirlipede increasingly roll for competitive purposes, for many intrigued challengers have tested their pokemon against the Whirlipede in at first unwitting "races" which are as much obstacle courses as contests of speed, and the Whirlipede have so eagerly taken to this competition that they have begun to race one another even with no humans around.