Happy Birthday, Sean Penn!

The notably intense actor/director is 51 today, Aug. 17. He may be most notorious as Madonna’s ex-husband, but there are a lot of other things about him you probably don’t know. Check these out:

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His first professional appearance came in 1974, when he was 14. He was a blond-haired extra on an episode of “Little House On The Prairie.”

He Didn't Always Play Cops Or Bad Guys Who can forget his role as stoned surfer Jeff Spicoli in the 1982 movie"Fast Times At Ridgemont High?" He wore a lot of zinc oxide on his nose and rescued Brooke Shields from drowning.

He Really Gets Into His Roles For 1986’s "Shanghai Surprise," his movie with then-wife Madonna, Penn reportedly learned Mandarin Chinese. Too bad it was a wasted effort; the movie still stands as one of the worst ever.

It's Not You, It's Me Penn was married to Madonna from 1985-1989, but the union was marred by persistent reports of drunkenness, violence and Penn’s alleged addiction to pornography. (Bonus trivia: In the beginning of their relationship, Madonna and Penn thought there was a magical connection between them because their birthdays were one day apart.)

He Listens To The Boss Penn directed and wrote the 1991 film "The Indian Runner," a bleak tale of two brothers, after hearing the song “Highway Patrolman” on Bruce Springsteen’s album “Nebraska.”

Strike Two In 1996, Penn married actress Robin Wright, and although the relationship had none of the public displays of the Madonna days, the two went through some bad times, separating, reconciling, filing for divorce and reconciling. They finally divorced in July of 2010, agreeing to have joint custody of their 17-year-old son, Hopper Jack.

He's Not Afraid To Play Gay In the 2008 critically acclaimed film Milk, Penn played gay rights activist Harvey Milk, the first openly gay politician to be elected to office in California. His mother, actress Eileen Ryan (left), was pretty happy with the movie.

He's Won The Oscar Twice Despite his reputation for offscreen hell-raising, Penn takes his acting very seriously. In 1995, he won an Academy Award for his portrayal of a killer facing the death penalty in "Dead Man Walking," and in 2003 he got the nod for his part in "Mystic River" as ex-con Jimmy Markum.

Tell Us What You Really Think Penn’s never been shy about his political views. He wrote an antiwar letter to then-President George Bush , calling Dick Cheney and Condoleeza Rice “criminally obscene people.” He’s also become friendly with leftist Venezuelan President Hugo Chavez. This prompted Chicago White Sox manager Ozzie Guillen, a Venezuelan-American, to invite Penn to see the “real Venezuela” and “see how long you last, clown.”

He's A Great Organizer Penn does more than issue abrasive political announcements. After the earthquake in Haiti in 2010, he founded a nonprofit group that operates two refugee camps containing 50,000 people. In the months following the earthquake, when the effort to get people help was mired in bureaucracy and disorganization, human-rights observers said Penn’s camps were the best organized and most highly functioning in Haiti.