Rounder

Rounder (ラウンダー) is a flying enemy in Mega Man 5, which basically looks like a flying eye. They appear in groups of three at the end of the first stage from Proto Man's Castle, right before the boss gates. Rounders were supposed to attack enemies while moving around them, but as attack functions were forgotten to be installed, they just circle around Mega Man and interfere with his shots (which could be dangerous since it appears along with Subeils that also appear near the end of said stage). Rounders can also crash into Mega Man if he jumps before they begin to circle completely. They can be easily destroyed with the Mega Buster or Water Wave, but if ignored for a sufficient amount of time, they will eventually fly away.

Rounder II
Rounder II (ラウンダー2) is a modified version of the Rounder in Mega Man 6. A pair of Rounder II are the boss for the first stage of Mr. X's Castle, at the top of what seems to be the outer wall. They run back and forth on a rail while dropping bombs and trying to hit Mega Man. They are vulnerable to the Flame Blast and a charged attack from the Power Adapter, which is able to change their direction.

Other media
Rounder appears in the first episode of Mega Man: Upon a Star, being one of the robots that attacks an amusement park in Japan and combines into Samurai Man.