@Hector Gomez
Other countries phase out old notes as they wear out. They also make them illegal tender a period after a new design is introduced.

I assume the US do, and would do the same; although not being American, I don't know.

I wouldn't go so far as to say they're something out of Hogwarts though. As people have suggested, there are some weirder and wonderfuler(sik) notes around the world employing interesting security and design measures.