In this episode, a suprise worker evaluation test is held at the Power Plant, and Homer fails it. This was hilarious as the replica work station manages to blow up even though there was no Nuclear material in it. He is then forced to go back to College in order to keep his job. He goes to Springfield University and takes Nuclear Physics 101. This was also hilarious because of this scene:
Teacher: "Hello students, I see we have many new students, but as the old saying goes out with the old in with the nucleus"
(everyone laughs except Homer)
(Teacher drops papers; Homer laughs so hard, but he's the only one)
This scene along with the scene where he puts his GED on fire make for a classic episode. Overall, one of my favorites and one well worth watching. 10/10 A+