Back in November, we took a look at the worst inventions from some of history's most famous inventors -- stuff like Leonardo Da Vinci's water-walking shoes, Thomas Edison's ghost-listening device and Alexander Graham Bell's obsessive quest to breed six-nippled sheep (how do you feel about your precious cell phone now?). Perhaps not to be outdone, contemporary inventors have also been up to some pretty strange shenanigans, from Dean Kamen's air-powered human cannon to a little something called the turd twister.

Even though famous inventors have left lasting legacies of useful devices, it's still true that the vast majority of things get invented by people you've never heard of, from salaried men and women toiling away in corporate labs to university professors, plus the occasional bright 12-year-old. Many inventions are recycled from other things, and some have been dreamed up by people famous for other accomplishments. This includes the bifocals and stoves invented by Benjamin Franklin, and Thomas Jefferson's work on dumbwaiters and swivel chairs, which the third president gave away free to the world a la open source.

Here we look at some surprising inventions by people who are much better known for other pursuits.

sir isaac newtonSir Isaac Newton and the Cat Door
Most people don't think of the late, great Sir Isaac Newton as an inventor per se, since he is best known as a theoretical mathematician and scientist who worked out the powerful physical laws underlying gravity, thermodynamics and optics. His work was also instrumental in developing calculus. Few people remember that, in addition to his affinity for falling fruit, Newton was an animal lover.

Although it's hard to verify that Newton was truly the first person to ever think of it, a number of sources record that the brilliant scientist was the first to employ a cat door for his beloved pets. As the telling goes, when Newton was doing experiments with light, his kitty would often nudge the door open, ruining his work. So he cut a cat door and covered it with felt, to block the light but allow felines easy access. An elegant solution to cats' "first you want out, now you want in" nature.
Margaret Thatcher and Soft-Serve Ice Cream
Tough-talking Margaret Thatcher is best known for her role as prime minister of Great Britain from 1979–1990, but the "Iron Lady" also had a softer side. In the 1940s, after she had graduated from Oxford, she worked as a chemist for J. Lyons and Co. She was on a team that helped develop a method for whipping more air into ice cream.

Ice cream sellers liked this new development because they could use fewer ingredients, and consumers took to the lighter, softer texture. Soft-serve ice cream could also be dispensed through a spigot, which made serving easier. So without ol' Margaret Thatcher, we probably wouldn't have Dairy Queen or Tastee-Freez. For her work changing the way we cool off on a hot summer day, Thatcher reportedly earned about $775 per year.
George Lucas and Digital Film Editing
Most casual moviegoers think of George Lucas as the main force behind Star Wars. Film buffs may revere the bearded one for "American Graffiti" or "THX 1138." But few people outside of the entertainment industry think of Lucas as an inventor.

In fact, in order to tell his epic stories with such sophisticated effects, Lucas had to come up with a lot of the filmmaking technology. He led teams of innovators that created the first digital editing system, so film would no longer have to be cut and organized by hand. His group also pioneered 3-D-rendering animation software, which was spun off to Pixar. According to the Associated Press, "Lucas sold many of his technologies for cheap -- technologies that would later appear in home stereos, cell phones, medical-imaging devices and virtually every Hollywood studio, driving billion-dollar companies and employing thousands of people." His film, video game and special effects companies continue to develop cutting-edge technology today.

Jacques Cousteau and SCUBA
World-famous oceans explorer, scientist, filmmaker and advocate Jacques Cousteau also had a major role in developing diving technology, though this isn't often remembered by a general public who grew up watching him on TV. With Emile Gagnan, Cousteau invented the modern demand regulator, which provides air at ambient pressure to users. In 1943, Cousteau and Gagnan began selling their so-called Aqua-Lung, which built on past diving designs (including work by magician Harry Houdini), but also offered new flexibility and comfort.

Hedy Lamarr and Frequency Hopping
Ever heard of Hedy Lamarr? Ask your grandparents. The Austrian-born American actress was a leading figure in Hollywood's Golden Age. She appeared in such major films as Cecil B. DeMille's "Samson and Delilah," "Ziegfeld Girl," "Boom Town" and "Tortilla Flat." She appeared in an Andy Warhol film in the '60s, and has a star on the Walk of Fame.

But Lamarr was also a brilliant scientist. In 1942, she and a friend patented a system of frequency hopping, which was designed to guide torpedoes and help them evade detection. The technology was eventually adopted, although after the patent ran out. Today it is still in use in cell phones and wireless networks.