From WiKirby, your independent source of Kirby knowledge.
Booler is a floating ghost-like enemy which appears in early Kirby games. It resembles a Boo from the Mario franchise, though it does not behave similarly. It flies about in various patterns, either going in straight lines, circles, bounces, or seeking Kirby directly. Booler can appear out of thin air under certain circumstances.
Kirby's Dream Land
Booler makes its first appearance in the first Kirby game. It appears in Castle Lololo as well as Mt. Dedede, where it can be seen in a large variety of different flight formations. Booler can be inhaled, but is worth 400 points when defeated by other means.
In the Extra Game, Booler is replaced by a similar enemy named Gaspar.
Kirby's Pinball Land
Booler appears as an obstacle on the Kracko stage of Kirby's Pinball Land. It flies around a Gordo and is worth 360 points when hit. Hitting them is necessary to call a Warp Star on that floor.
Kirby Tilt 'n' Tumble
Booler reappears in Kirby Tilt 'n' Tumble, appearing in some boss stages. It will try to pursue Kirby when provoked, and will need to be lured away from the areas it guards in order to progress.
Kirby's Dream Land sprite