1. You can tell how big a guy's penis is simply by checking the size of his feet or hands.
While this would make finding a date easier, there's absolutely no basis to this one whatsoever - despite how many women might wish otherwise. A British medical journal published a study asking this very question in 2002. After studying several hundred men, they found there was absolutely no relation whatsoever between the size of one's feet and the size of one's penis.

2. Guys think about sex every 7 seconds.
As hard as it might be to convince anyone who's ever known a horny college student, guys actually do not think about sex every 7 seconds or even every 30 seconds. Even thinking about sex once a minute works out to an incredible 960 times a day, not counting sleep time. Based on the Kinsey Report, an amazingly detailed study about human sexuality that changed how the public thinks about sex, about 53% of men think about sex several times a day. The amount goes down from there, with roughly 4% of guys only thinking about it less than once a month. Let's be generous and assume that "several" means 5 times a day, which comes out to be about every 192 minutes or once every 3 hours they spend awake.

3. The baby on the Ivory Soap box grew up to become an adult movie star.
It wasn't the baby who later went into adult movies, but the mother! Marilyn Chambers was working as a model when she was photographed for the Ivory Soap box holding a baby. A few years later, she went to an audition for a small screen part. When she realized it was for an adult movie, she would have left if the producers hadn't talked her into staying. Marilyn got a prominent role in Behind the Green Door with a frisky lesbian scene and one of the first prominent interracial scenes in the adult industry. When Ivory Soap learned about her new adult career, they quickly dropped her as a model despite Marilyn's belief that they would start selling a lot more soap.

4. There's a pill you can take that will give you orgasms.
There's no such as a dedicated orgasm pill, but there's at least one drug on the market that can lead to orgasms as a side effect! Clomipramine was an antidepressant drug that hit the market in the mid-1990s. Soon after, the Canadian Journal of Psychiatry reported that about 5% of users (both male and female) experienced orgasms whenever they yawned. The experience was so pleasurable that the affected users would regularly attend boring meetings and were reluctant to stop taking the medication! But before you run out to try to pick some up, Clomipramine actually makes it more difficult for 95% of people to have an orgasm.

5. Sylvester Stallone starred in an adult movie.
In his very first movie role, Sylvester starred in an adult movie called Party at Kitty and Stud's. As Stud, Sylvester earned $200, a fair sum for a struggling actor in 1970. He got a nice blowjob from Kitty and gave her a light spanking and even took part in a foursome with some of Kitty's galpals. The movie was heavily cut before being released, leaving a lot of the more explicit material on the editing room floor. In other words, Stallone fans might be a little disappointed that he doesn't show more. While most adult stars find it hard to go back to a more mainstream career, Sylvester didn't have that problem. Only a year later, he starred in Woody Allen's Bananas before landing his role in Rocky.

Thanks to Snopes.com for helping to debunk and prove these urban legends.