Ururuun

Ururuun (ウルルーン) is the miniboss in Grenade Man's stage. It's a giant eye that attacks by tackling Mega Man or dumping junk above him. It surrounds itself with layers of junk which can be destroyed. It surfaces from the junk pile that is it's arena.

Trivia
It's name is derived from the Japanese onomatopeia "ururun", which describes drooping, weeping eyes. Defeating it gives you the rush motorcycle