We "stole" a lot of ideas for this site actually and also expanded on other people's ideas. My son and his friend are 1 week apart so we do their birthdays together. For their 9 year old birthday we did a backwards/upside down/inside out party. The invitations were done backwards, type(do mirror/transfer image on printer), and folded upside down and backwards. I did leave "frontwards"; and really small; "if you can't read me hold me up to the mirror".( one mom calle dto get the info cuz she lost it and later founf it in the bathroom :) They were addressed to the backwards names of all the kids. Our favorite was Dorfdarb (Bradford).  I got balloons printed with "happy birthday", and turned them inside out(I used the non brush side of a toothbrush to do it),and hung them from the ceiling; a clear table cloth printed with "Happy birthday" and just put it on the table upside down on top of a cheap colored table cloth; and plastic "Party's here" signs, taped to the windows... backwards of course. We had all the kids wear their clothes backwards and missmatched (some even wore them inside out) and crazy hair.  First we had "moon pies" instead of cake and pudding-which they had to eat with only a straw-instead of ice cream. We played pin weird stuff on the donkey. musical chairs, where we only took chairs out and went when the music stopped. ( that was a little dangerous- but funny). and spin the bottle/charades( when the bottle/bowling pin landed on them they had to act something out. THey got empty bags at the beginning and filled them as they went through the party. I would suggest getting extra bags as some were "lost" (how in one room of the church, they did it I don't know)Then we had pizza in bowls, and poked holes in the bottom of soda cans( with an awl and hammer) and I found cheap crazy straws to put in them that the kids got to take home. We opened presents somewhere in the middle of all the chaos.  One present was wrapped with the ribbon tied on the present, then wrapped with the paper inside out!! So fun!!! The whole thing was really fun, and my friend and I had just as much fun as the kids!!