Pope John Paul II shows up for the unveiling of The Homer.
This episode probably takes place in August, because in the episode "Brother, Can You Spare Two Dimes?" The magazine date says August 11, 1991. Since kids were never said to have to go to school in this episode there is no doubt that this episode takes place during summer vacations.
The scene of Bart using the word "bastard" to describe Homer's long-lost half-brother (with Bart defending that it's the correct usage of the word ["bastard" meaning "someone born from unwed parents"]) was edited when shown on UK's Sky1 channel and BBC Network.
The failure of The Homer is based on the failure of the Ford Edsel built by the Ford Motor Company from 1958 to 1960, the vehicle was considered as a failure for Ford due to poor design features and poor sale figures.
When Herbert tells Homer "As far as I'm concerned, I have no brother!", it is a reference to the film The Godfather.
The Shelbyville Orphanage director looks a lot like Dr. Julius Hibbert, and since he stated that he had spent years searching for his long lost brother, it is a possibility that the one he's looking for is actually Dr. Hibbert.