There is this church about a block from my house, i did the following to it last year: The congregation and the priest was going on a walk "to admire gods work" (I call it zoned development) during the service, I ran in with my friend and began to make duct tape pentagrams on the walls while my friend pasted saten posters on the alter. On the way out we poured washable fake blood all over the floor (left over from last Halloween), and poped Bill Nye The Science Guy into the massive over head projector. We then waited on the other side of the street. When they came back it was so funny. People running every where with water screaming with Bill explaing how the universe began in the back ground. Then the police arrived and I swear i saw one laugh when he herd he irony of bill nye I will try to find the video tape we made form the other side of the street.
PS: I shared this as a response to another person in another thread, this post contains more info.