Most unique birthday party activities for kids?

What is the MOST unique activity you have seen at a birthday party for a child? (Or for an adult -- my husband and I have theme parties a few times a year and can always use ideas!) I'm pretty creative when it comes to party planning, but I am just wondering if anyone has ever seen anything that just blew your mind. Thumbs up if they include dinosaurs (the theme of my son's upcoming birthday) and ten points for best, most unique answer (I think I finally figured out how to pick a best answer here!)