The mission starts at the Noiseland Arcade. First, you have to talk to Apu and ask him to help you defeat the aliens. After he chickens out, you have to speak to Otto, who is standing nearby. You have to drive the School Bus, picking up all 17 children on the way to Krustylu Studios on time. You will complete the mission when you arrive at Krustylu Studios where you turn to Barney to start the next mission.
Getting Down with the Clown
At Krustylu Studios, talk to Barney and ask him where Krusty is. After Barney tells you he's down at the Squidport, you need to hop in your car and follow the truck promoting the new Itchy and Scratchy Movie (you'll know which one you have to follow as it has a yellow arrow hovering over it). It will stop outside the observatory where Krusty's limo is. You need to go to Krusty's limo and talk to his chauffeur. As you approach him, he will drive off, luring you into a race to the Squidport (my advice is not to get out and talk to him, but to ram your car into Krusty's limo. The chauffeur will step on it but you will have to stay in your car, saving you time and giving you a better chance of winning. You will complete the mission when you arrive at the Squidport. Go over to Krusty to begin the next mission.
Lab Coat Caper
This mission is simple. Basically, talk to Krusty to warn him about the free laser guns that are being distributed around the Squidport. After he doesn't believe you, you try to think of someone who could prove it. You think of Professor Frink. You need to get into your car and follow Frink in his hover car to the observatory (I recommend using a fast car). He will try to lose you by going the long way around everything. You will complete the mission when you enter the observatory where you will see Frink. Talk to him to start the next mission.
Duff for Me, Duff for You
Talk to Professor Frink in the observarory, explaining that no one believes you about the alien conspiracy. He believes you, saying it "explains the strange transmissions he's been getting on his Plutonium CB Radio". He says that the aliens are hiding lasers in the Duff trucks. When you've finished your conversation, head to your car and head to the Duff Brewery (you have to get there in under 45 seconds). Once there, you will see a Duff truck full of lasers park outside the other gate. You have to ram into it and pick up 6 lasers. After that, rush back to the brewery in the allocated time (it varies) and find a laser to show to Krusty, which is on top of one of the boxes underneath the Duff Blimp. Mission Complete! You then go to the taffy shop by the container ship and talk to Principal Skinner to begin the next mission.
Full Metal Jackass
Talk to Principal Skinner at the taffy shop and explain to him the lasers and aliens but he confiscates the laser you found for Krusty. To get it back, simply destroy his car (he isn't that fast so it should be easy) and get it back. To complete the mission, simply retrieve the laser. Head up to Krustylu Studios and speak to Krusty to begin the next mission.
Set to Kill
'TO COMPLETE THIS MISSION, YOU WILL NEED TO PURCHASE THE GLOBEX SUPER VILLAIN CAR FROM KEARNEY AT THE KRUSTYLU STUDIOS ENTRANCE FOR 600 COINS. Up at Krustylu Studios, speak to Krusty and show him the laser where he finally believes you. However, he says that you that you should have told him before he let them set up free laser stands around the level. Head over to Kearney to buy the Globex Super Villain Car for 600 coins. Once bought, exit Krustylu Studios where you will find the first stand. Keep destroying them until you get to the final one. Then, go back to Krustylu Studios in less than 50 seconds and speak to Krusty for the final time where you will complete the mission. Then, head up to the Krusty Burger opposite The Android's Dungeon and speak to Homer where the final mission of level 6 will begin.
Talk to Homer and explain to him that the aliens have taken over the Duff Brewery. Outraged, Homer reveals that he never sold his old car so Bart could go to college. Homer and Bart have to race the aliens that are driving a black sedan to the Duff Brewery. Once there, you will have completed the mission where a movie will roll.
Bonus Mission- Milking the Pigs
The mission starts by talking to Snake, who is walking along the path opposite the gas station by the staircase. He wants you to destroy Chief Wiggums' car, to obtain evidence against him. get into your vehicle and destroy Wiggums' car and go back to Snake. He then wants you to destroy a milk truck, because Fat Tony gives 'big money' for it. Head down to Barney's Bowlarama where you will find the truck. Destroy it and go back to Snake where you will complete the mission. Your reward will be the Lil' Bandit, Snakes' car.