The company Monsarno is a reference to the real-life company Monsanto
This episode has the final appearance of Edna Krapappel, because Marcia Wallace passed away on October 25th, 2013.
Next to a picture of Edna in the final scene of the episode is a picture of Maude Flanders, Ned's first dead wife. Ned's black armband confirms that Edna was killed off in an unknown fashion. In the episode, Ned says that Edna signed him and herself for tango lessons.
The license plate on Marge's car reads "SABF07", which is the production number of this episode.
The name of Willie's mop is Ethel.
Pun licence plates that Sideshow Bob was printing: