This episode marks the first appearance of The Seven Duffs. However, only Tipsy, Queasy, Surly and Remorseful are named in the episode.
The second Duff Gardens commercial shows Dolph, Jimbo, and Kearney getting arrested, yet they reappear near the end driving bumper cars into the sunset. In that shot it can also be seen that the "E" in "Duff Gardens" looks like an "F".
Lisa's underwear exposes when she's seen getting off the couch after Homer says that they were all going to Duff Gardens.
We learn Barney Gumble is a sperm-donor and is a father of untold amount of children.
On the magazine, "101 Frozen Pops", Professor Frink, Jacques, and Troy McClure (which is ironic, given that Selma would be with Troy McClure in "A Fish Called Selma") are featured, likely sperm donors like Barney.
One of the movies Homer and Marge watch while Homer is sick is The Erotic Adventures of Hercules, which was mentioned on "Mr. Plow" when Troy McClure hosted Carnival of the Stars.
This is one of the few episodes where Patty and Selma show no disgrace to Homer, this was even shown when they raised their hands (along with Bart, Lisa and Maggie) for Homer to flash forward through Aunt Gladys' will reading.
The Seven Duffs are a parody of the Seven Dwarves.
After hearing about the Sweathogs Selma said, "I checked, it isn't Horshack". This is a reference to Ron Palillo's character on the sitcom "Welcome Back, Kotter".
According to the DVD commentary, the end scene with Selma and Jubjub is a reference to the Murphy Brown episode, where Murphy's son Avery was born, which was a highly rated sitcom at the time this episode first aired.
In the first shot that shows Dolph, Jimbo, and Kearney stealing the bumper cars, Jimbo's bumper car is blue. In the next shot, Jimbo's bumper car changes to green.
While Lisa is intoxicated after drinking the "water" in Little Land of Duff, her skin tone alternates between a sickly pale greenish color and the normal yellow. When she is walking along with the parade, her skin is green, but when she starts dancing in front of the cars, her skin is yellow again. When she is returned to Selma by the security guards, her skin is green again. When she gets back from Duff Gardens with Bart and Selma, her skin is yellow again, but when she says "Can't talk, coming down", her skin tone has settled on something in between the two tones.
People have to be 21 to drink alcohol. You cannot market children or people under 21 for alcoholic beverages at a theme park. Duff Gardens should only be for ages 21 and up. Therefore Bart nor Lisa should have not been there.