The snags they sang were added into the script by the writer to include songs by artists who verbally identified themselves as "freaks." IE-david Bowie, Lana del Rey, fiona Apple, nirvana, etc. That's why some of the songs they performed (well all of the songs) were written AFTER the freakshow era (1945-1960). The show got a bunch of harsh reviews by fans for including a nirvana song or songs by artists who didn't see fame until 20-30 years after the freakshow story..but there are two main things going on there. The first being what I already mentioned that they were songs performed by people who identified themselves as freaks..and secondly if you listen to the lyrics of the songs that were performed they also relate to the backstory of the freak that was performing them. Nirvana "come as you are" is a song about social acceptance and not conforming to the mainstream patterns of society and just being the person you were born...no labels or gimmics or trends..and that's really what Jimmy stood for. Think back to his convo with dandy where he spoke about how he would give anything to have normal hands and not scare girls away to live a life in the shadows because he is a "freak"...same with criminal by the twins..it went along with them killing their mother..and all of the songs Elsa performed tied into her storyline and there was even a song cut from the show by Kathy Bates that tied into Ethel's storyline! I know I got a little off topic from the intention of your post but I just wanted to add this because it's something people seem to gripe about a lot but I don't think people fully understand why Ryan added those elements to the show!!!