In the forward to the book, David poses a question regarding whether an axe that has had its handle replaced and head replaced is the same axe you had when you first bought it, at first this seems like a philosophical non-sequitur, after finishing the book you realize he is actually asking whether he is the same person he always was after being replaced by a clone from the other world.
OK, so Korrok is artificial intelligence gone horribly wrong/4chan/a troll and Shit Narnia is the internet. Of course kittens are used for medicine, and will make the sad go away. Cats are the patron animal of the internet, after all. Lolcats are basically their health system.
At the beginning, Dave mentions that he didn't know his real father, and that Arnie could be his father for all he knows. He asks Arnie if he is his dad, which Arnie denies, looking at Dave a bit weird. This look makes much more sense when we find out that Arnie is a ghost of a black man, who Dave only sees as white because of his expectations.