June 27, 2009 -- He was Michael Jackson. He could do anything.
So when fans saw him do the impossible on the dance floor, they never thought he had help.
But when the King of Pop and his dancers leaned at a gravity-defying 45 degrees in live performances of the 1987 hit "Smooth Criminal," it was a secret gimmick -- not super-human talent -- that made it all possible.
A patent filed with the U.S. Patent and Trademark Office in June 1992 lays it all out.
Naming Jackson, Michael L. Bush and Dennis Tompkins as the inventors, the patent describes a "system for allowing a shoe wearer to lean forwardly beyond his center of gravity by virtue of wearing a specially designed pair of shoes which will engage with a hitch member movably projectable through a stage surface."
That's a complicated way of saying the dancers' shoes had heels with slots that can hitch onto pegs that protruded from the stage at predetermined times. The pegs retracted back into the stage after the move was executed so as not to impede the performers.
"Music entertainers and dancers are constantly searching for new and interesting elements which can be incorporated into their musical and dance performances," the patent reads. "Interesting stage design, lighting, fog generators, laser light shows and large video screens all enhance the appealability of live and recorded performances."
"Many popular music and dance entertainers expend great effort in enhancing and choreographing their performances and dancing," the patent document says.
New Design Let Dancers Execute 45-Degree Lean in Live Performances
Previously, entertainers used cables connected to harnesses around the dancers' waists to create the ant-gravity effect. But, the documents say this system wasn't possible in live performances and also restricted arm and body movements.
The document goes on to say that the new design is similar to footwear worn by astronauts working in zero-gravity environments.
While Michael Jackson's "moon walk" was far and away his most famous move, the "Smooth Criminal" lean certainly ranks among the legendary dancer's most memorable.
'Smooth Criminal' Featured on 1987 'Bad' Album
"Smooth Criminal" was one of the hit songs on Jackson's 1987 "Bad" album, which sold 22 million copies internationally. It was also included in his film "Moonwalker." In 1988, it was released as a single and hit the No. 7 spot on the Billboard Hot 100 list.
The song is about a woman named Annie who was attacked in her apartment.
As of Friday evening, "Smooth Criminal" had hit the seventh slot on Apple's iTunes top songs list and a YouTube video of a two-year-old radio edited version of the song had attracted more than 16 million views.
Jackson's music also grabbed nine of the slots on the top 10 albums list on the site, with "The Essential Michael Jackson" in the No. 1 spot.