Wallis, better known by his nicknamed "Puffy Pants Wallis", was a space pirate. Ratchet fought him at the Voron Asteroid Belt. His ship looked like a skull and his main attacks consisted of a large, red blade which would fly around the screen, a barrage of homing rockets, and a straight beam of energy from his ship's 'mouth'. His ship's weak point was accessed by shooting his right eye when it opened. (Occasionally, the player may see Wallis waving inside the eye, implying that its weak point was in fact the window to the control room of the ship.) This only happened for a limited time, though.
Before Ratchet faces puffy pants Wallace Aphelion refers to puffy pants Wallace's ship as a pirate demolition vessel.