|Time(s) Available:||before curfew|
|Unlocks:||Nerd Boss Fight|
Stronghold Assault is the first storyline mission in Chapter 4.
Algie and Pete are in the Library. Algie is explaining to Pete that the Nerds won't let him join their clique because they find him weird. Jimmy walks in, ignoring Pete, and asks Algie for help taking down the Jocks, but Algie suddenly turns unfriendly. He compares Jimmy to a bouncer and says the nerds are above helping people like him.
After Algie leaves, Pete advises Jimmy to bring the Nerds back in line by taking on their leader, Earnest. Jimmy leaves to do so, Pete asking if he can go with him for once after Jimmy's out of earshot.
The route to the Observatory is beside the Library, guarded by a door that operates with a keycode. Thad is guarding it, but he gives up the keycode after taking a single punch.
Behind the door is a grassy area. The Nerds hide behind trees, rocks, and on top of hills, firing on Jimmy with firecrackers, stink bombs and bottle rocket launchers. He fights his way through them and finally comes to the Observatory gates. Earnest has rigged up a rapid-fire potato machine gun. Jimmy has to shoot out the mechanism that makes it run. Once he does, Earnest retreats inside the Observatory and locks the door.
Jimmy has to take control of the potato gun and use it to break down the doors of the Observatory. Nerds appear in the windows and on the roof of the Observatory, throwing firecrackers and forcing Jimmy to shoot them as well. The door has a life bar like a boss. Once the bar is empty, the door flies open and the next mission starts automatically.
The game isn't prepared for the possibility that Jimmy may bring a bicycle to the route leading to the Observatory. If a bicycle is used to travel to the Observatory before Earnest has finished making his threats, the potato gun will be unmanned and it is possible for Jimmy to use it to break the doors. Once broken, the doors can be walked through, but the building itself is inaccessible. Switching to Jimmy's view beyond the entrance reveals a very modest version of the building's interior that is blocked by an invisible wall.
The mission can be continued normally if Jimmy backtracks and lets Earnest speak the rest of his threats before returning to the potato gun. Earnest will be using the potato gun normally and disabling the gun ends the mission since the doors are already broken.
- Thad tells Jimmy that the code to the lock is 1138. This is a reference to George Lucas' signature easter egg.