The Drill Boulder is a gimmick from Mega Man 4, found in Drill Man's stage. It is a large boulder that drops from chutes and shatters upon hitting the ground.
Drill Boulders returned in Make a Good Mega Man Level 2, and were used in the entries Cardinal Man, Joe Destruction Co., Gunpowder Cellar, Bouncy Castle, and Guts Man's Asteroid. They also appeared in the Wily stage Reality Core, the Pit of Pits sublevels "Logan's Runner" and "Magic Crash-Pit Ride", and in Null and Void.
Drill Boulders are created by Drill Boulder Spawners. If Mega Man gets close enough to one such spawner, it will create a Drill Boulder that quickly falls to the ground. When it lands, it breaks into four smaller rock pieces that disappear upon hitting the ground and are capable of hurting Mega Man. If shot before hitting the ground, however, Drill Boulders will not create any rock fragments. If he remains close to the spawner, it will produce another Drill Boulder provided that one (or its rock fragments) isn't already present onscreen.
In Make a Good Mega Man Level, Drill Boulders will simply explode as opposed to shattering into small fragments; this behaviour is preserved in Make a Good Mega Man Level Remastered.
- Drill Boulders were initially named "drillman_rock" in Make a Good Mega Man Level's devkit.