Bet you couldn't even hear any of the sound effects in the final battle from how insanely loud the music is, but they're there. He reuses lots of sounds from elsewhere in the game. www.mediafire.com/file/6v29cv...
I really liked the idea of Pizzaface being a devilish Pizza creature instead of being a mech controlled by PizzaHead. Pizzahead just feels like if you gave the Noise godlike powers to prank everyone. Also: Pizzaface moving sfx sounds like a washing machine lol.
Personally i like the idea that while Pizzaface is a mech, him and Pizzahead are still separate entities that can act on their own. During levels is when theyre working together and its an instant kill, the fact that you beat Pizzaface during the fight is due to, as we see, pizzahead just not paying attention and ignoring whats going on. Supporting my theory with the fact that even after you defeat him, pizzaface still comes back to help pizzahead during the second phase