This might be the funniest thing I've ever read on c|net:

Christmas period... hike in service calls due to incidents such as the classic backside copying prank. Such a stunt, a mainstay of the office party, often results in cracked glass on the copier, with 32 percent of Canon technicians claiming to have been called out to fix glass plates during the Christmas period after attempts to copy body parts went wrong..."

Silly kids, let me impart some advice to avoid broken glass in the ass (heh that rhymed).
Don't put your weight on the copier, you want to hold on to the edges of the copier and have all your weight on your hands, with the ass area just barely touching the glass. This will ensure an injury free copying experience.
[disclaimer] How do I know so much about the topic? ...No comment : P