what's up with my 6 year old?

So we are going trunk or treating this Friday at the Hoosick Falls Alliance Church. We had not planned to do anyhting after many lengthy discussions, but decided this was easy enough and was a good way to get the kids out and doing something! (Plus then we do not have to buy candy to hand out! I know, I am cheap!) Anyway...after I told the kids we were going, we all decide to look in their rooms to find costumes because I am not spending money on anything! (Again...cheap!) It was easy enough...there is an abundance of spider man and superman pjs, light sabers, and hunting supplies inthis house! And Anna wanted to be a bunny...simply wear grey sweat suit, tape ears on a headband, add a little face paint and pin a tail on - VOILA - bunny! RJ can't decide between Spiderman or superman - or bob the builder, but we have the hat! And John wants to be a soldier. Andrew on the other hand...he comes to me and says, "I want to be a platypus." WHAT? I don't even know if I can spell that right (did I?) How can I make a costume like that out of what we have in the house? So...I am asking for any creative ideas you may have! LOL!