Buttons McBoomBoom is a cold-blooded hitman that serves as Big Boss' bodyguard. He dresses and talks like a 1930's gangster. Under his suit, housed in his cybernetic torso, he possesses twin machine guns.

Buttons absolutely hates bugs of any kind, will open fire with his twin machine guns at the very sight of one. Buttons also has a philosophy about not killing people. He instead prefers to break his adversaries down, letting them live.

Buttons is an extremely superstitious criminal, and he treasures his lucky penny, the first cent he ever stole. One day he lost his penny, and Big Boss gave him a fake, telling him that he found it. During a heist with Turbo Tu-Tone, Buttons learned the truth when he found that Longarm's son found it.