Well, if you want to continue your previous theme, you could fill your underwear with high-intensity red and amber LEDs, and have the Arduino flicker them while it generates a fizzling sound...
I have to wonder why you're asking this in April, though. Is Halloween rescheduled among the Norse because of the risk of little trick-or-treaters getting frostbite if they go out in costume on 31 Oct?
thx for the tips so far..
I have to go something "new" (new for me).
The haloween is not moving no, but I want to have a a lot of time to play with the outfit.. Also I will have to import stuff, so customs use time, etc.