Miho and Kevin are both former assassins that were trained by the ColonelThey both have similar skills and are crazy enough to be involved in The Guild. They escape for moral reasons (Kevin, as twisted as he is, had some bizarre moral hangups). He ends up at the Farm while Miho decides to hide out in Old Town.
Wallenquist is the Nazi Hunter in "Rats"This Troper has seen this theory before on other sites. A younger Wallenquist is hired by the German mafia or government to exterminate the retired Nazi war criminal and that's the start of his organization. For all we know, this story actually takes place in Germany and not in Sin City at all.
Marv is still alive.If Superman can come back from the dead, why can't this guy just have been put in a death like trance when he was electrocuted...then woke up when he was stuffed in the cremating machine and broke out.
Kevin is a Vampire.We never see him in direct sunlight, performs his killings in a lightproof room under the farm, has supernaturally sharp fingernails and agility, and finally, doesn't die until he's beheaded. If nothing else, being a Malkavian fits him wonderfully.
The characters who reveal their full names are the only ones in the whole city who are without sin.Everyone who goes by One Name Only, and they are many, are harboring some guilty secret or other. Wallace likely did something in that war except win the Medal of Honor, and he's a fairly straightforward hero compared to most of the protagonists. Nancy Callahan is an innocent and John Hartigan is Galahad incarnate. Dwight McCarthy's case is a little curious; if memory serves we only learn his last name after he dies and gets resuscitated, symbolically cleaning his slate - not that he ever forgives or forgets his murder of Damien Lord. And Ava Lord, she might only wear Mr Lord's name as a disguise. "Iron" Jack Rafferty, though, is the exception. Unless he's aware of the rule and taking advantage of it to get good press to hide his true nature? Yes, I just Epileptic Tree'd my own Wild Mass Guessing.
The '57 Bel Air was manufactured well past 1957 in the Sin City universe.As the story goes, a bunch of pissed of GM executives struck out in late 1957 to make their own '57 Bel Airs in several small factories in Southern Illinois upon finding out the '57's iconic bodystyle, with its famous peaked tail fins, was being axed for the next year. They made them, though only coupes, with hand pounded body panels (which fixed the imperfections in Fisher's mass production) and frames, transmissions and engines pirated from Illinois Chrysler factories, then sold to used car dealerships across the US, and supposedly over 200,000 were made. Or course in reality it's pure rot, but this could be stretched to making sedans, wagons and Nomads as well, which would explain why there are so many in Sin City, being used as police cars, taxis and private vehicles.