This episode (aired on January 05, 2020) marks the fifth decade The Simpsons has been on (1980, 1990, 2000, 2010 and 2020).
Couch gag: The Simpsons enter and sit on the couch and are turned in to a coin which Nelson places on a railroad track to be flattened by a train which he follows with his signature "Ha Ha" before being hit by a train himself.
Chalkboard gag: "Teacher spent New Year's Eve at home by choice"
The billboard outside the school reads, "2020 Eyeglasses: We Don't Help Your Vision, It's Just the Year"
The title is a reference to "Hail to the Chief"