Burlesque AU! Frisk is running away from home when she comes across a club called the Underground. After meeting a dancer from inside who claims he wants to help her, Frisk gets sucked into a world she never imagined herself being a part of. When she's forced to become one of the girls by the club owner, an unlikely protector steps up to shield her from harm. {Mostly Sans/Frisk}

Chara reigns as kingpin of the biggest mafia branch in the underground. Twin sister Frisk stumbles into the corrupted world, torn between the dangerous life of a mobster and working undercover for the FBI. Under the watchful eyes of vigilante Sans, rookie Papyrus, special agent Undyne, and more, Frisk will either fight for justice… or fight for survival. Undertale Mafia AU.

Frisk is once again sent to another universe and gets involved with crime. Meanwhile Sans has to take care of a younger, quieter Frisk who has their own problems. (Crossover story with nyublackneko's Undertale Mob AU. Light Sans/Frisk. Part of the Road Trip AU series. Oneshot)