Don't flush the toilet when you are sitting on it!!
This is what I heard on Mix Megapol - Stockholm (Local radio station in Stockholm).
An American woman onboard a SAS plane en route to New York went to the restroom. When she was going to flush, she remained seated and the vacuum toilet created - that's right - a vacuum in the lavatory and she couldn't get up. She had to sit there the rest of the flight and after laning in New York (read EWR) technicians were able to get her out of there. I wonder if the technicians could keep themself from laughing.
The woman has been economically compensated by SAS.