Helluva Boss/WMG
Mammon is the embodiment of Greed
Seeing as Asmodeus is ruler of the Circle of Lust, so it makes sense that the other Seven Deadly Sins would have Anthropomorphic Personifications. While Mammon has not been physically seen, he seems to be an industrialist and capitalist, marketing things like cereal, soft drinks, and everything in Loo Loo Land. Fizzarolli literally sold his body (presumably for money) to Mammon in order to become the mascot of these products, and is now a cyborg as a result, something he seems just fine with. Also, Mammon's portrait seems to be on Hell's currency, although in the episode where this is implied, viewers can not see it, as Blitzo's thumb was covering that part of the note in the brief scene. The designation of Embodiment of Greed could fit very well.
- Confirmed
The kid in the pilot was not the correct mark
Fans of the series know that the IMPs’ mark in the pilot is an obnoxious foulmouthed child; despite this, they are reluctant to kill him until he is confirmed to be the actual mark. However, right before he is confirmed as such - by Loona - he insults Loona, calling her a dog and saying he's a cat person. Loona is clearly very offended by this; then she reads a text on her mobile, and tells everyone else that it’s from their employer, telling them the kid is indeed the mark. Could she have been lying in order to give them all an excuse to kill him?
Beelzebub was Evil All Along
This is a theory posed by fans who looked into “Queen Bee” and compared it to the lore introduced in other episodes. On the surface, Beelzebub is a Nice Girl, a generous philanthropist and gracious host who does not share the common disdain demon nobles have for the lower class; imps and hellhounds are welcome at her parties. On the surface it seems she is, at worst, Affably Evil, as while she is clearly feeding off the emotions caused by her guests' indulgences and gluttony, she isn’t being a jerk about it. But certain factors hint as a darker side to it. In addition to being behind Hell’s production and sale of liquor, she heads what passes for their Department of Child Services, and childhood for hellhounds is miserable. Orphanages for hellhounds double as pounds (meaning most residents of Hell regard them as little better than animals) and it’s even hinted that, for a lot of them, “adoption” means “slavery”. The parties certainly serve to give them a sense of self-worth, but it also likely results in them having children, which in turn leads to more hellhound children abandoned and neglected by “the system”. Bee is, in effect, keeping a vicious cycle going in order to more easily create the emotions she feeds on. It gets even worse when you consider that she is the embodiment of Gluttony and her rather horrific true form. It is possible the pleasant public facade is her way of suppressing her true nature, which if left unchecked, would cause her to become a mindless abomination what would hunt and devour her subjects.
Loona was Sexually Abused as a Child
A very dark theory, yes, but there are some hints. In the pilot, Blitzo gives her a gift and she asks, "Is it a cure for syphillis?" Everyone assumed this was a joke at a time to troll Blitzo, as the show is big on Black Comedy. But a later episode shows she spent most of the first eighteen years in her life in an orphanage that looked far more like a prison (which also doubled as an animal pound) and syphillis is a disease where symptoms manifest ten to twenty years after infection. If Loona was serious about having the disease, the best case scenario is that her mother had it while pregant with Loona, but if not, she might have been assaulted sometime as a child, which makes her past even more miserable than it already is.