We often say, "in case of" to mean if there's the situation that. When he says, "in case you didn't know," he expects you to know, but he wants to be sure you know.
It's easier to say, "let it snow" here when we're out of school than in Norfolk or New York. Do you like snow? How deep is the deepest snow you've ever seen?
Is this song too fast or confusing? Do you think the song writer is really egotistical, sensible, cynical, or something else? Do you think many people want to pretend they are someone different?