Seven friends once pulled this at my college cafeteria.
One put a hot water bottle filled with pea soup down his chest;
he sat at the head of a table, with the other six friends
sitting along the sides.
When the cafeteria was pretty full of people,
he made a loud noise (to attract attention),
stood up, bent over and squeezed his chest.
This caused a huge gush of green liquid to spew all over the table;
the other six immediately began to eat this green liquid.
I think a lot of food went uneaten that night.