I'm not sure when this episode came out, I think after TPM came out.
I only saw it once, so I'll try to explain as best as I can.
Basically there is the big hype of the long awaited "Cosmic wars" movie.
Then they go in, and the movie starts. The opening crawl comes up and it is like 5 paragraphs about trade tariffs and legislature, then the whole movie takes place in the senate where palpatine reads off the names planet by planet about their rights, or something.
Then bart and Lisa are pissed so they go up to sky walker ranch to *****, and the also take a tour. They made lucas like 3 feet tall, and they basically mocked him (I forget what they said).
When they are on tour they go to the creature shop, and every body gets all excited.
Then when they get there it is just a guy in a CG motion capture suit standing in front of green screen and every body is disapointed.
It rings true a lot (mainly about TPM crawl which was odd at the time), but I never found these bashing lucas/SW things that funny.
Basically because there is really nothing funny about it. It is just a guy writing and making movies just like everybody else. So when they bash about it, its almost like they have nothing to make fun of.