Duon

Duon is a boss that is encountered late in The Subspace Emissary. It doesn't hail from any particular series and is unique to Super Smash Bros. Brawl.

After Snake, Meta Knight and Lucario kick all of the Mr. Game & Watches out of the Halberd's cockpit, they dissolve into Shadow Bugs, which form into Duon. Duon is a large robot with two upper bodies protruding from its base. One of these bodies has a blade for a head, while the other has a laser. When one head takes damage, it turns 180 degrees and presents its other head.