How do "costume change" magic tricks work?

This could explain how, but not for sure since its a general explanation not specific for katy perry.

She starts off wearing three outfits each made of extremely thin material. Each outfit is convertible, meaning it can be changed quickly. For example you can have a short white skirt that is actually a long colored white dress but is pulled up (folded in half) and the normal bottom is now part of the blouse. Each outfit gets converted 2 or 3 times then they send her behind a screen, or in a tube of material where she can make that outfit disappear. After all the outfits are used up they hold the dish full of confetti above her head and drop it (Notice the dish disappears). That is because the dish is another dress INSIDE OUT. When they drop it the confetti masks the view of her raising her arms into the dress and slipping it on over what she was already wearing. Notice at the end the bowl holding the confetti is gone and she has confetti inside the dress that she is trying to blow out just as she comes back into view.

Naw! Old hat. 1. There are other names you can't create folder or files. Because it is a reserved word. Others are: Name Function ---- -------- CON Keyboard and display PRN System list device, usually a parallel port AUX Auxiliary device, usually a serial port CLOCK$ System real-time clock NUL Bit-bucket device A:-Z: Drive letters COM1 First serial communications port LPT1 First parallel printer port LPT2 Second parallel printer port LPT3 Third parallel printer port COM2 Second serial communications port COM3 Third serial communications port COM4 Fourth serial communications port 2. The notepad did not work on my computer. Mine is a Vista. You probably would get obscure ascii characters on older versions. 3. That is a know quirk for MS Word. It is created by the font programmer in the beginning. Open any font in your font folder and you get that same sentence. Sorry to burst your bubble bub!