Fry, Leela, Bender, the Professor and Richard Nixon are the only characters to appear in both this episode and the series pilot, "Space Pilot 3000."
When Bender and Fry arrive in robot hell, The Robot Devil and his minions are playing the song from "Hell Is Other Robots."
Preacherbot mentions the power vested in him "by the state of New New York." Up until this point, it had never been mentioned if the state's name had changed along with that of the city's. However, it was marked as such in the episode "Bendin' in the Wind."
On the spinning wheel that the Robot Devil uses to select what robot hands Fry shall switch his hands for, the names are actual names of robots that have been on previous episodes (and/or this episode). The robots found on the wheel (in order of appearance) are the Robot Devil, Billionaire-Bot, Flexo, Daisy Mae 128k, Crushinator, Roberto, Helper, Kwanzaabot, Robot 1-X, Clamps of the Robot Mafia, Hedonism-Bot, Fat-Bot, Linctron, Destructor, Robot Santa, Joey Mousepad of the Robot Mafia, Tinny Tim, Spinny Chins, Chain Smoker, Angleyne, Sandra, Execu-Tor, Reverend Lionel Preacherbot, Washbot, Fembot, Hair Robot, Unit 2013, Donbot of the Robot Mafia, Frankie, Boxy, Lulubelle 7, Humorbot 5.0, Calculon, Officer URL, Foreigner, iZac, Cartridge Unit, Barkerbot, Teenbot, Gearshift, Q.T. McWhiskers, Deep Blue, iHawk, Cylon, Patchcord Adams, Liubot, Stage Mom 7.0, Sinclair 2k, Vending Machine, Oily, Coolometer, Andrew, Monique, Rab-Bot, Lisa, Executive Gamma, Keg Robot, Greeting Card, Eurotrash 80, Nannybot 1.0, Emotitron, Jr., Ceiling Fan, Hookerbot 5000, RectalExam-Bot (on whom Bender bets), and Bender (whose name shows up several times on the wheel). Interestingly, several of these robots do not have hands.
In the season three episode "Parasites Lost," Leela mentions how only a few people in the world could play the holophonor, and even then they weren't very good at it. However, many of the children in Fry's class appeared to be quite good at it.
A running gag for the episode features the Robot Devil saying something is ironic and Bender pointing out it isn't, culminating with him pointing out something that is ironic.
Every time Fry plays the Holophoner (except when he is composing and playing his opera), there's the snail from "The Grumpy Snail" in the holograms. The snail also made an appearance in Fry's Holophoner record commercial.
The Robot Devil had the same teacher as Fry does now.
The theatre where Fry plays a piece is called "HoverCar-Negie Hall"
During the intermission, just after the Robot Devil gives Leela Calculon's ears, she asks if he is going to take her hand. The Devil robot holds her left hand and tells her to go enjoy the opera. When the angle changes he's holding Leela's right hand.
Fry, Leela and Bender are the only characters to appear in every episode of the series. In second place are the Professor and Doctor Zoidberg who both appeared in 70 out of 72 episodes. The Professor did not appear in "Where No Fan Has Gone Before" and "The Why of Fry"; Doctor Zoidberg did not appear in "Space Pilot 3000" and "Mars University".
The windows in Fry and Bender's apartment keep changing positions.
When Bender tells Fry to "get your coat", Fry is already wearing it, just as he always does.
During the opera, Beezlebot picks up the Preacherbot and pulls him on stage. In 1ACV09 "Hell Is Other Robots", Preacherbot keeps saying how evil Robot Hell and the devil are, so it is a bit odd that he does not react to being picked up by Beezlebot.
Fry appears on the album covers for his music shown in the TV ad Zoidberg is watching with his own human hands, not the devil's robot hands.
Bender opens his safe marked 'Bender's Loot' some how from the inside where the door has no handle/combination on the inside.
All of the parents protesting Bender are fathers (or F.A.R.T.ers). Mothers, apparently, have no such issues with Bender.
The other kids at Cubert and Dwight's "cool party" are the same orphans that Bender adopted in The Cyber House Rules. There is also a Horrible Gelatinous Blob kid present, though it's presumably not Bret Blob (the blob who bullied Dwight and Cubert in Route of All Evil), unless they've patched up their differences since then.
Opening theme promotion: CONTROLLING YOU THROUGH A CHIP IN YOUR BUTT SINCE 1999
The human character on All My Circuits is named "Human Friend".