FBI!Sans: me, just kinda an average lonely Colorado guy.
FBI!Flowey: FBI!Sans' roommate... without limbs. FBI!Sans kinda just makes him all the food and stuff.
FBI!Toriel: FBI!Sans' gf. the simping station.
FBI!Spamton: the annoying ass boss at FBITale
FBI!Papyrus: FBI!Sans' goofy ah meme bro
FBI!Jevil: A really nice chill guy at FBITale (so nice everyone forgets about him)
Ness: FBI!Jevil's pet Plessie. the reason that FBI!Jevil's relevant here.
LuCk3y: a maniacal cyborg grunt from madness combat that just kinda goes around destroying shit in Denver
Sir Amogus III: was meant to be undyne but i suck at drawing undyne. basically just undyne, except sus?
Hackara: chara but hacker
Super Mafia Bros: Your local gang. Temmie is calm, just a meatshield really. Madjick is also kinda calm but he has a tank so people are scared of him. Jevil is insanely insane to the C O R E.
Mafia Bros lore: Jevil got beat up by the party and REALLY didnt like that. So he grabbed lancer's bike and went to the undertale universe to get a team, where he met temmie (who loves the bike) and madjick. he tried to go back to the deltarune universe but went to fbitale instead (he created FBI!Jevil while doing so.) now they just beat up guys in Denver.