Many famous actors aren't satisfied with their stardom, and they want to do something more. Over the years, a handful of actors have truly made a difference in the world "“ and in some cases, they did so in ways that you wouldn't expect. From inventors to troublesome mistresses to Kevin Bacon, here are seven examples.

1. Lola Montez "“ She Ended an Empire

Few 19th-century entertainers were as colorful as Irish actress and dancer Lola Montez (born Eliza Rosanna Gilbert), who appeared in Broadway shows and performed around Europe as a "Spanish" dancer. She was also banished from Warsaw for publicly criticizing the ruling despot, attacked a newspaper editor in Australia when he published a bad review of her show, gossiped with the Tsar, and was the lover of composer Franz Liszt. In her most notorious episode, she became mistress of King Ludwig I of Bavaria in 1846, despite a 35-year age difference. Her fierce temper and arrogance made her very unpopular with his subjects, who were furious to see the influence she held over the famously amorous king, especially when he made her Countess of Landsfeld. Noble or not, her scandalous behavior contributed to the fall from grace of the popular king (who had ruled for 22 years), inspiring thoughts of revolution. Ludwig was forced to abdicate in 1848. Montez died in 1861 at age 39.

2. John Wilkes Booth "“ The President's Toughest Critic

booth.jpgMany actors have strongly condemned the president of their time, but only one actually shot his commander in chief. John Wilkes Booth's most dramatic performance, leaping to the stage after killing President Lincoln in 1865, might have overshadowed his acting pedigree. Despite the legend, he was not a failed actor. Born in Maryland, he was the younger brother of Edwin Booth, who brought class to the American theatre with his intense renditions of Shakespeare. John won his own renown as a dashing Romeo, and made a popular tour of the South in 1860-61 at the onset of the Civil War. The brothers (along with a third brother, Junius) also did a memorable version of Julius Caesar (with John playing, you guessed it, Brutus) not long before the assassination. John had entered into a conspiracy plot, and he famously shot Lincoln at Ford's Theatre in Washington D.C. Though he escaped on a getaway horse waiting at the back of the theatre, he was shot twelve days later at age 26.

For the record, Edwin's career went from strength to strength, despite the stigma of being an assassin's brother. His later renditions of Othello in Britain, alongside the great English actors Sir Henry Irving and Dame Ellen Terry, won large audiences and rave reviews.

3. Florence Lawrence "“ Auto Pioneer

florence-lawrence.jpgCanadian-born Florence Lawrence is mostly forgotten, but devoted film buffs remember her as the world's first movie star. Initially, like all movie actors in the early days, she was uncredited for her work, and known to her fans as "the Biograph girl" (named after the studio that made her films). Though her face became famous, her name was unknown until Hollywood mogul Carl Laemmle brought her to his new IMP Company in 1910, revealing her name in big newspaper ads. At her first public appearance, in St. Louis, the crowds she drew were bigger than those that had greeted President Taft the previous week.

In her spare time, however, Lawrence was a tinkerer. The daughter of inventors, she was one of the first car-owners and a true automobile geek, inventing such accessories as the "auto signaling arm," a forerunner of the turn signal (she placed an arm on the back of the fender that could be activated with the push of a button) and the automatic "full stop" sign, an early version of brake lights.

Sadly, like Erno Rubik and the inventor of the wheel, her genius didn't extend to filling our patent forms, so others became rich by enhancing her inventions. Nor did she realize that popular film stars could demand ridiculously high salaries. She eventually died in poverty in 1938.

4. Zeppo Marx "“ The Cleverest Brother

Of all the Marx Brothers, the youngest, Herbert (alias Zeppo), got the raw deal. In the early movies, he played the straight man who usually didn't do much. He left the team when they moved to MGM in 1934 (when, it so happened, their box-office improved greatly). But before labeling him as "the boring brother," note that, as the baby of the family, he was stuck with that role. The others said that, in private, he was easily the funniest Marx. When Groucho was in hospital during one of their vaudeville shows, Zeppo would take over his role "“ and did it so well that some in the audience thought he was the "real" Groucho. (The cigars made him sick, however.)

Moreover, he was a brilliant engineer who always had a love of motor cars and machines. After leaving the Marx Brothers, he formed an engineering company, Marman Products, which manufactured coupling devices for aircraft. During World War II, most of his work was top-secret, but it was said that one of Marman's devices was used to hold the first atom bombs in place. Some years later, he invented and patented a wrist device for cardiac patients that measured their heartbeats, sounding an alarm if the wearer went into cardiac arrest.

5. Hedy Lamarr "“ Mastermind of the Wireless

There must be something about movie stars and inventiveness. Hedy Keisler made history with her teenage nudity in the daring Austrian film Ecstasy (1932), and won even greater fame when she moved to Hollywood and took the name Hedy Lamarr. In films like Algiers (1938) and Samson and Delilah (1950), she was known as one of the most sultry and beautiful women in the movies.

But Lamarr had brains as well as beauty. During World War II, she invented a radio guidance system for torpedoes, which she developed with the help of another clever Hollywood friend, composer George Antheil. Known as "frequency hopping," it consisted of two synchronized pianola rolls, allowing technicians to switch control frequencies so the torpedo could escape enemy tracking. Though they received a patent in 1942, the War Department declined to use it. It was later adapted for satellite communications, and is now widely used in cellular phones and other modern technology. As the patent had expired before most of this, neither Lamarr nor Antheil profited from their cleverness, but Lamarr was given due recognition before her death in 2000.

6. Eva Peron "“ Argentina's National Heroine

evita.jpgNot every world leader has a movie star background, but as the current French president has proven, it doesn't hurt to marry a popular entertainer. Argentina's Eva Duarte, the illegitimate child of a farm laborer and a coachman's daughter, escaped her village at age 15 for a career in show business. Her acting skills were nothing special, though she made six movies and became a popular radio broadcaster. Soon she was hobnobbing with political big shots, marrying revolutionary Juan Peron in 1945. They were a popular pair, with her good deeds (including work for charity and women's suffrage) softening his image as a charismatic but tough soldier. Her humble background was frowned upon by the upper classes, but it made her a hero to the poor. Within a year, Juan Peron was elected president, thanks in no small part to the popularity of "Evita" (Little Eva). Politically astute, Eva had a strong influence in her husband's government, and he wanted her to run as his vice-president in the 1951 election. Sadly, she had been stricken with uterine cancer and was too ill. She died, aged 33, in 1952. Naturally, she remained a folk hero in Argentina, and became even more famous as the heroine of the rock musical Evita (1978), which was filmed in 1996, presenting Madonna's best-ever film performance. When the movie was released, Madonna was already four years older than the real Evita had ever been.

7. Kevin Bacon "“ He Might Save the World Someday

bacon.jpgWell, sort of. Remember the 1990s party game Six Degrees of Kevin Bacon, in which players try to link any given movie actor, through a short chain of films, to Kevin Bacon, the star of Footloose and Mystic River? Bacon once commented in an interview that he'd worked with everyone in Hollywood, and three Albright College students created and popularized the game.

Of course, the idea of networking (getting a job from the friend of a friend) was nothing new, but around the time Six Degrees of Kevin Bacon originated, scientists Duncan Watts and Steve Strogatz were exploring the world of network theory, a new field of scientific research suggesting that large groups (be they viruses or football crowds) don't connect randomly, but are structured around nodes. The theory was all well and good, but they needed to prove it by studying some real networks. Strangely, few networks had been mapped "“ but then they discovered The Oracle of Bacon, a cheat-sheet website for the Kevin Bacon game, created by student Brett Tjaden and linked to the Internet Movie Database.

Tjaden's program, in the hands of the scientists, advanced the research considerably. Network science principles have already led directly to the capture of Saddam Hussein, as the military moved through the dictator's social networks. But there are hub networks everywhere from computer chips to human cells. In the future, it is hoped, scientists will map out networks to combat terrorism, predict pandemics, even cure cancer. When this happens, remember to thank a certain Hollywood star for an off-hand comment he once made in an interview.