Well, in 'larry the scary story', Larry might be a character that is central to the horror elements. Maybe he is a victim, or perhaps he is the source of the scariness. For example, he could be a haunted figure or someone who has stumbled upon a dark secret, which then leads to all the terrifying events in the story.
Since we don't have much information given, Larry in '600 lb life larry's story' is presumably an individual who has reached a weight of 600 lbs. He might be from anywhere, with different life circumstances that led to his extreme weight. He's on this show to document his journey of transformation. It could be that he has faced discrimination or has been unable to do things he loves because of his weight. His identity as Larry is tied to his story of facing the challenges of obesity and trying to overcome them with the help of the resources provided by the '600 lb life' program.
Well, a smut novel refers to a book where the focus is heavily on sexual themes and often has very detailed and graphic descriptions of sexual acts. It's not for everyone and is usually considered more adult-oriented.
I'm quite certain Larry wasn't in the original Christmas story. The original Christmas story mainly involves characters like Mary, Joseph, the baby Jesus, the shepherds, and the three wise men. There's no mention of anyone named Larry in the traditional accounts of the nativity.