Fighting the Zombiebot King:
In order to beat the Zombiebot King just wear him down using rockets until he pauses (does not move). Toss a grenade (coring charge) into its mouth - usually, it takes five grenades to kill him, and after the 3rd and 4th grenades there are regular zombiebots that swarm the arena.
Note from the dev team:
In the "You Know The Drill" level, tether the Predator. Then pick up a secret chip. Look at the mission objective in the pause menu for a note from one of the level designers. (The designer himself hinted at the easter egg in a GameFAQs MA: GitS board topic.)
Original Concept Movie:
To unlock the original concept movie, finish the whole Campaign (Story) mode.
