Mash (マッシュ,Masshu) is a giant clown-like robot that appears in the Robot Museum mid-stage in Mega Man 7, giving time for Dr. Wily to escape with the stolen Guts Man. He hops about trying to squash Mega Man, but Mega Man can hit his head to damage him and knock it off. If his head gets knocked off, Mash will hop erratically until his body can regain the head. This came from a mistake in it's design, even when Mash's design was supposed to be Dr. Wily's best. 
Mash is weak to the Danger Wrap, but it cannot hit him unless his head has been knocked off its body. The Thunder Bolt is his secondary weakness, and can be aimed with much greater effectiveness as it can knock Mash's head off.
Mash appeared in the Rockman 7 manga in a role similar to the game.
In the Rockman & Forte manga, King created an improved Mash with the data he stole from Dr. Wily. Mash is one of the robots King sent to attack Wily's base. He was destroyed by Mega Man.