The Surprise Core is a bipedal mech piloted by a pig, with a frontal opening protected by a series of small barriers. It is fought in a shoot 'em up section, with the battle consisting of two phases.
During the first phase the Surprise Core will turn to face the player and unleash a barrage of lasers. The player must pass through the one gap in the lasers to avoid them, and destroy the barriers protecting the pilot. The boss will eventually move to the left and turn around.
Once all barriers are destroyed the Surprise Core's legs will explode and the second phase will begin, as the boss flies to the center of the screen. It will extend four segmented arms which will spin around, retracting and extending them every now and then.