Grinder is a parody of Grindr, a homosexual geosocial app.
Julio drawing in red on a map, showing a travel route, could reference to the film series Indiana Jones by Steven Spielberg, which almost always has a scene similar to this.
A lyric in the song 'Decommissioned' in which Smithers sings is similar to a lyric in the song Count on Me by Bruno Mars. (specifically, "Waiting on you 234" to Bruno Mars' Count on Me "I can count on you like 432").
In point of fact, this song appears to be a very clever joke; It's both a parody of Count on Me by Bruno Mars, while simultaneously being a reference to the Nuclear Plant (specifically, because of the half-life of the radioisotope of uranium, U-234 and more vaguely, because the Nuclear Plant is where Smither first met Mr. Burns and the Nuclear Plant likely produces Uranium-234 as a direct result of the decay of [non-fissile] U-238.) When Smithers sings the words "I've spent half of my life, waiting on you to 34," what he's referencing is the half life of uranium (U-234).
Rob LaZebnik mentioned in an interview that the inspiration for this episode came from his relationship with his gay son, Johnny LaZebnik, who came out during high school.
This episode shows that Springfield is located in the middle of the United States. This could be also deducted from "Much Apu About Nothing". Both chapters suggest that the Springfield from the United States which corresponds to the fictional Springfield in The Simpsons is the one from Colorado. However, Matt Groening has revealed that the town was named after Oregon's Springfield, and in "Eternal Moonshine of the Simpson Mind", it is shown that the Simpsons' Springfield is the one from Illinois. This contradictory evidence might suggest that Springfield is just a fictional place with no precise location in the Simpsons Universe, as one of the many coherence issues in the show.
Smithers officially comes out as gay in this episode, after being in the closet prior to this episode.
Smithers also attempted to come out in three prior episodes: The first was in "Bart's Inner Child", where, during the Do What You Feel festival, Smithers attempted to admit his romantic love for Mr. Burns, only to quickly change gears and claim he was actually loving the shirt Burns was wearing at the time, causing him to ruefully state he should have come out to Mr. Burns at the boathouse; the second was in "Lisa the Skeptic", where Smithers, believing the end of the world was occurring, chose to kiss Burns on the lips, but when it turned out the doomsday warning was a publicity hoax, Smithers quickly covered himself and stated it was "a sign of respect." The third was in "Homer Defined" when there was a nuclear meltdown occurring, Smithers told Mr Burns "There may be another time to say.. I love you, sir." to which he replies, "Oh, hot dog. Thank you for making my last few moments on Earth socially awkward.".
This is currently the last appearance of Lionel Hutz, who makes a cameo appearance in the school auditorium during the play. Since the death of his voice actor back in Season 9, Hutz has since been retired and reduced to non-speaking cameos.
At the Licenses Bureau, it is possible to see for a fraction of a second that the official gives Smithers and Julio a marriage license, but later, it is a completely different fishing license.
Janey mis-says her name as Jacqueline Jones. It is quite possible that it is her real name and that 'Janey' is a diminutive of 'Jacqueline', although she has been given different surnames in other episodes as well.
In the map that Julio shows Smithers, the USA is separated from Canada and Mexico is surrounded by the sea.
It is possible that Julio only drew USA and Cuba because he just wanted to show Smithers the journey to Cuba and the other countries were unimportant.