http://www.etsy.com/shop/SIMONEmadeit (I know the link isn't working within my text but I promise that is the correct link, so copy and paste it. Sorry about that.)
We sent out fun invitations that said for Secret Agent Eyes Only. We gave each child a new agent name. Each name was a color and animal. My daughter was purple monkey. For the party we referred to all children as their secret agent names. To get into the party they had to decode the password (It was awesome sauce.) and do a secret handshake. We decorated with finger prints and mustaches.
First thing they had to do finger prints (this went into their goodie bags to take home.) The whole party was set up to complete missions to earn a Goodie Bag. First Mission was a laser maze. We had the girls hang out in my daughter's room. To get access to the bag yard they had to go through the laser maze.
Other missions included finding letters in rice and creating words with those letters, target practice (shooting golf balls off a railing with a nerf gun), and popping balloons and using secret pens to decode a message. (We were having way too much fun to remember to get photos of each mission.)
In the end everyone received a goodie bag filled a pen that wrote in invisible ink, a notebook (inside my daughter wrote a thank-you note with the special pen),a necklace with a picture of the code name (purple monkey, golden hyena, blue horse), candy, and magnifying glass.
We also served truth serum (water), pizza, and bombs (cupcakes).
This was by far my favorite birthday party that I did for my daughter.