Mobtale: a summary.
As seen before with Underfell, some UNDERTALE iterations could be better described as a whole category of AUs with similar traits. Such is the case with "Mobtale," or Mobstertale, wherein the common threads are that while monsterkind was never banished from fresh air, tensions with humankind have persisted to the point of monsters forming gangs to get by, and either the 2010s still maintain the style of the so-called "Prohibition Era" or the entire 2010s population is set back ~80-90 years.
While Mobtales can be distinguished from Undernovela by cultural differences between transatlantic USA and Latin America, Mobtales can also be distinguished from each other by monsters' jobs, dealings and relationship with humans.
Take, for example, "UT Mob AU" where human children had been experimented upon by adults to incite tensions between humans and monsters. The children were meant to be taken in by monsters as Trojan horses, and then triggered to collect their monster SOULs. Asgore and Toriel had lost their son this way, not knowing what had been done to Chara. W.D. Gaster had been researching how to rehabilitate Frisk and others before them, and Alphys was entrusted with continuing their treatment plans after his passing, but his brothers Sans and Papyrus, who used to work for Toriel but now work for Asgore, unknowingly intercepted a delivery when they found Frisk in a crate.
They did not recognize Frisk as a human but saw they wore a dog tag, which said FRISK. 349-550-0 C-TEST, so the brother nicknamed them "Little Pup" or "Lil Pup." As much as Toriel wanted to take over upon seeing Sans' and Papyrus' inexperience at childcare, she compromised that she'd help the two provide for them since Lil Pup took a liking to staying with the two at their abandoned warehouse.
Sans began investigating in secret, but after there'd been a failed attempt to mug Papyrus at knife-point, Lil Pup later attacked Sans with a knife. Papyrus intercepted and diffused the situation, and Lil Pup would not remember this incident, but Sans was still wary. He tried once to return them to the humans, with Temmies to lead the way, but he couldn't follow through when Lil Pup cried for him. So he took them back home, committing to his and Papyrus' responsibility for the child, and resumed his investigation.
Alphys would tell him everything when it led him back to her, but word about the "pup" had reached Asgore through Undyne, at which point he put out a dead-or-alive capture order. Sans intercepted the dog monsters, but Papyrus intercepting Undyne set Lil Pup off and Sans would take them both elsewhere before they could take Papyrus' SOUL. In the following struggle, Sans stole Frisk's SOUL as they were stealing his, and in the panic to preserve Frisk's, the two's SOULS osmosed to a degree before Sans Frisk's body would accept theirs back.
After this incident, Alphys was able to explain the situation to Asgore, and he called off the headhunt.
...In the case of "Undermafia," Sans and Papyrus work for W.D. Gaster, who in turn refers to Frisk as "young boss." The Skeleton Family was entrusted with the human's care when Asriel died and Toriel feared what Asgore would do after their separation. W.D. Gaster especially took a liking to Frisk, while Sans' motives are more financial and Papyrus is a reluctant but proficient sniper.
Meanwhile, in "UT Gangster AU," Sans and Papyrus, fronting as an Italian diner alongside Grillby, work for Toriel after the loss of Asriel motivated Asgore to found their gang. Asgore remains the gang's public face and Undyne acts as underboss, usually with Sans on diversion duty and Papyrus as the getaway driver. This... frequently means that Sans lets the police target him for brutal physical abuse. He does not give them the satisfaction of seeing how much they're hurting him, but he does not tell the gang what he endures for his them either, which has forced Papyrus to feign ignorance around Sans' secrets. Depending on where else alterations have been made, this AU especially could also suggest that staying on the surface has allowed monsters to emulate more physical matter– enough to bleed. Because this Sans has. Often.
As seen above, another major disctinction between Mobtales is custody of Frisk. Frisk is Asgore and Toriel's formally-adopted child in both Undernovela and Undermafia, but in UT Gangster AU they were not taken in permanently until after they tried turning Frisk in as a runaway, only for them to return to the Dreemurr family; and in UT Mob AU, it was Sans and Papyrus who adopted Frisk, being the two who found them. This is the more overt differentiation.
To understand a more subtle difference for telling apart Mobtales by their Frisks, it must first be understood that as organic lifeforms, humans have historically related identities and social designations to their external tissues, such as how adults use some of these traits to assign genders to newborns, assign social roles to genders and maintain social pressure to follow these birth assignments even into adulthood. By 201X, more human societies have begun phasing out these gender roles, but Mobtales take after a time period several decades earlier.
This may give context for the variations in Frisk's presentation between Mobtales. In UT Mob AU, they were never forced to follow this practice under the care of monsters, whereas in UT Gangster AU, they'd gotten in frequent trouble for mixing gendered school uniforms until they were homeschooled. And in Undermafia, Frisk is what other humans would call a tomboy, addressing herself as a girl while dressing more like the men and boys of the time. This could be due to the underdeveloped vernacular of the era's mainstream or to fundamental differences in her sense of identity.
...Come to think of it, I don't know whether or not assignment should also go on the list of alterations. Back in my timeline, it never came up before I ▢▢▢▢▢▢▢▢▢▢, and I had no reason to review our Frisk's personal data when I went looking for □□□□.
