Go to Homer's bedroom and click on Homer's desk, on the bottom right corner of the screen. After that, click on the right drawer and you should be able to pick up and keep a note. Go to the nuclear power plant and go to Sector 7G. You should now be able to pull the lever on the wall in the upper left part of the screen. A rope will fall -- pull it. Turn the light as it appears. Finally, get the donuts.
AREA - OBJECT/LOCATION Krusty's Office - Krusty key in money drawer at Town Hall. Skinner's Office - "Spanky" key in lost and found box at Moe's Tavern. Cemetery Telescope - In e-mail on Skinner's computer. Miss Hoover's Bottom Drawer - Paper in Lisa's desk drawer. Gerbil Cage - Gerbil food in Miss Hoover's bottom drawer. School Lockers - Slip of paper under Bart's bed. Grampa's Bottom Drawer - Paper in Bart's locker. Stone Cutters - Ring in Grandpa's bottom drawer. Mr. Burns' Washroom - CMB key in Stone Cutters. Other - Book in Stone Cutters can make Flanders' kids act possessed
Go inside the television room at The Simpson's House. Look in the bottom left hand corner to see a tiny bit of light coming through. Click on the light and you will appear in the Simpson's Backyard and Bart's Treehouse in clear view. You will also get to chuck water balloons.
In the main room of Krusty-Lu Studios is a "Labor Laws" poster hanging above a water fountain. Click on it to find a collector card underneath. Leave for a couple seconds, then return. Click on the poster again. This time a different card will appear. Repeat this process until all 74 cards are collected.