Beetlejuice never speaks his own name. It's implied he can't — otherwise, he could summon himself whenever he wanted.
This might be part of the reason he gives himself alternate personas in the cartoon, like Grimdiana Bones, Uncle BJ, and Sherlock Homely to name a few.
The Musical has him outright say he can't speak his own name, either to summon himself or to make it too easy for him to tell others to summon him. He has to give the Maitlands a card with his name on it and does the charades bit from the movie with Lydia (though actual charades rather than the magical version from the film because of the limitations of a live show). It's implied he can't even spell out his own name in one of the songs. While he does eventually spell out "Beetlejuice" during the song after messing up once, that's not actually how his name is written (just how it's pronounced).
Death causes paperwork for the Celestial Bureaucracy that is the Afterlife. Suicide causes more death, which causes more paperwork. Therefore, suicide victims - who had killed themselves with the hope of either ending their pain, or possibly getting to heaven - are punished for causing more paperwork by having to file that paperwork during their time as ghosts. It doubles up to teach them that suicide doesn't end your problems, while at the same time not condemning them to Hell.
Juno mentions that Betelgeuse used to be her assistant. It might seem odd, but there was a scene cut for time that showed he committed suicide by hanging because he was rejected by his lover. He was condemned to be a civil servant, until he went rogue.
Beetlejuice's small amount of sympathy for Lydia might also stem from what is implied to be his own loneliness: he doesn't seem to have any friends, he's desperate to marry someone and gets a bit too personal with his "clients." Even a creep like him can understand the feeling of having no one in your life.
Why are there hauntings in the first place? Ghosts have to have numbers and paperwork and case workers to handle all of that. Think about it; people who die go somewhere ultimately, but even completely accidental deaths like the Maitlands have to spend 125 years waiting for something - waiting in the living world.
If Otho, Charles, and Delia couldn't see the Maitlands, why did they hide out the window when the three of them came into the attic? Because Lydia, who could see them, was with them. She probably would have given them away and if their handbook suddenly disappeared, it wouldn't have looked good.
In the musical, Delia sings "there are spiritual guides above - look up! - and see 'em" to Lydia during her big number, "No Reason." At that very moment, Adam and Barbara are in the attic, and Beetlejuice is on the roof.
Also from "No Reason," while Lydia is generally dismissive of Delia throughout the song, she gets sharply angry when Delia tries to deny her claim that "Earth's a small place where good people die." Given that Lydia's depressed due to her mother's death, she likely took Delia's denial as an assertion that her mother wasn't a good person.
The Maitlands have difficulty understanding the book, while Lydia understands the book after reading it, and Charles is able to understand the guide to living with spirits. Adam and Charles says “it reads like stereo instructions”, and it explains how they are able to read it or not: The Maitlands are small town people and clearly don’t have a stereo (Adam listens to music on a tape player). Lydia and Charles understand the books because they’re from the big city, and more than likely have interacted with stereo systems more than the Maitlands have.
Betelgeuse's Kmart line became very dated when the company filed for bankruptcy and there are very few stores left in the United States as of 2022. However, there's another way the joke could work. After all, you could say Kmart is a dead company...
While talking about his qualifications, Betelgeuse claims to have attended Juilliard. This might actually be true: Betelgeuse has a penchant for theatricality and showmanship, so him going to Julliard, a prestigious performing arts academy that has produced great minds such as John Williams and Kelsey Grammar, isn't a stretch.
People retain the physical state they were in when they died. We see people hanging from nooses and flattened by cars. Imagine what happens to people who are blown apart or otherwise reduced to tiny fragments.
Well, Adam and Barbara were supposed to have died when their car fell into a river, but they're not wet. But that's a production matter, so I don't know if it counts...
They were wet when they first got home but dried off. Presumably only actual damage is permanent, but stuff inflicted by the environment like water or dirt can be cleaned off.
While Betelgeuse's backstory was cut from the film, it's implied by the fact that suicide victims become paper-pushers in the afterlife, and he used to work with Juno. In the original script, he hanged himself while drunk because a woman broke his heart.
So that finger with the ring belonged to her?
If that’s her finger, does that mean he killed her before committing suicide? “She meant nothing to me,” indeed...
What if she died first somehow and that's why he killed himself thinking they'd be together again. Might further explain his going rogue after finding out what happens to people who commit suicide in the afterlife.
It's even worse if it isn't the woman who broke his heart, because that means he has tried this before and failed, implying he killed the last woman with whom he tried the marriage thing. Either that, or she cut off her own finger to get away from him.
The Jockey is part of the ensemble in 'What I Know Now' in the musical. She died because she whipped a thoroughbred (horse). On her costume, hoof marks can be seen on her torso and head. This implies that the very youthful sounding jockey (played by a then-15-year-old Presley Ryan) died from having her internal organs or skull crushed by a horse
Adding to this, the hoofprints are only on the left side of her body, implying that because she whipped the horse, it threw and then trampled her.
Being a jockey, she would presumably know not to whip a thoroughbred right? Unless she intentionally whipped the horse, knowing it would be a death sentence.
While in the movie, ghosts stick around the human world for a while before moving on, in the musical the Netherworld is all there is in terms of the afterlife and it’s really... disappointing, dissatisfying, and eternally underwhelmingly depressing. While Lydia may have found joy in life, and while the Maitlands may have found peace, Lydia’s mother is still in the Netherworld.
And what’s worse: the Netherworld is expressly stated to be the fate of everyone who has ever died. Good, evil, or otherwise, everyone will end up in that dreary place eventually.
What's worse? You can't leave the Netherworld once you enter. While the movie implied (and the animated series demonstrated multiple times) that ghosts could leave the Netherworld, this doesn't occur in the musical. Beetlejuice and Juno outright say that ghosts who enter the Netherworld can't come back. Unless you're a demon like Betelgeuse, or a human who wandered in, you're stuck there. Worse yet, ghosts are told in the Handbook to proceed directly to the Netherworld once they meet their demise. Do you have any unfinished business or just want to stick around, but didn't get the chance to finish reading the Handbook? Sucks to be you!
Even worse is the Handbook is written in such a way that even if the book instructs the dead to head directly into the Netherworld, they wouldn’t be able to understand it.
Juno in the musical is changed to an Obstructive Bureaucrat who wants to keep the still-living Lydia in the Netherworld simply because the rules state that "when you go to the Netherworld, you don't come back." Is Lydia really the first human to get lost in the Netherworld and trapped there because of circumstances beyond her control? Miss Argentina frantically warns her and Charles to escape before Juno sees them, making this possibility all the more likely.
The skeletons in the office. It is impossible to skeletonize before death, so that implies the dead keep decomposing after death. Also, Beetlejuice himself looks rotten, despite having hung himself, so either you keep rotting or going rogue makes you rot.
This might seem pretty obvious, but keep in mind that in the musical, Beetlejuice only talked Lydia out of her suicide solely because she was the only living person who could see him and break his curse, not out of the goodness of his heart. What would've happened if Beej wasn't on the roof when he was? Considering when the Maitlands arrive on the scene, they'd never make it in time, so chances are Lydia would've succeeded in throwing herself off the roof and killing herself. Charles would have to spend the rest of his life living with the fact he unintentionally drove his daughter to her death because he was closed off when she needed him the most, and right after a major family tragedy. Delia would have to spend the rest of her life knowing she caused her future stepdaughter to do something so terrible, because she was insensitive enough to say the wrong thing at the wrong time. While Lydia would end up as a ghost, Barbara and Adam would still have to spend eternity with the fact they couldn't help her when she needed it and they were too late to stop her, and Lydia would be unable to interact with the world of the living. Maybe Delia had a point about how everything happens for a reason?
The movie makes it clear that the football players died in a bus crash. The musical, however, makes no reference to it. Instead, in "What I Know Now," when all of the newly departed list off what caused them to die, the football player says "Nietzsche was right, y'know. To live is to suffer, bro!" In the modern day, Nietzche's Darker and Edgier philosophy is heavily associated with antisocial behavior and many a Straw Nihilist. During the dance break in the song, more football players emerge (and they later chase down Lydia at Juno's behest), all of them wearing charred uniforms. What if the lead football player bombed his school?
Given that the crash the football players were in was so bad as to kill them all, it's easy to imagine that the coach who survived probably has some serious life-changing injuries. Not to mention enormous survivor guilt.
The Maitlands are childless and a bit sensitive about it, and Adam suggests they "try again." This suggests they were having trouble conceiving, which is already sad... but it's also possible Barbara suffered a miscarriage and they quit trying to conceive after that because it was so painful. This would make it even worse that they died when they did, right when they were ready to try and get pregnant again.
Juno is adamant that there can be no proof that existence continues beyond death, and she has a major point; without death as a final resolution, life ultimately has no meaning because it doesn't technically end. Additionally, there would likely be a massive increase in suicides as people try escaping their circumstances permanently (only to wind up part of a huge backlog of employees for the bureaucracy). There's also the worry that greedy businessmen might succeed in exploiting the ghosts the way Charles plans to, and with much more malicious intent.
Since suicides are forced to become the afterlife's bureaucrats, oppressed minorities who killed themselves like African slaves and Holocaust-era Jews thought they would be freed... only to be essentially enslaved anyway. For all eternity.
Are the people who jumped from the towers during 9/11 forced to be coworkers with the plane hijackers?
Just imagine the sheer horror on the faces of the Jews who killed themselves to escape the concentration camps and Geli Raubal (Hitler's niece, assuming she did kill herself to escape his abuse) when they found out Hitler himself would be joining the office forever.
Many people who committed suicide genuinely needed help in life and had sympathetic (though still wrong) reasons for what they did, like they couldn't fight depression anymore, they couldn't deal with bullying/abuse, or a birth condition or a terminal disease made life miserable. Imagine their sheer despair at finding out that the afterlife has absolutely No Sympathy and is condemning them to shuffle through a forever-growing pile of paperwork for the rest of time.
