Sean Penn, Charlize Theron were hot and heavy at Madonna's annual Oscars after-party. There is speculation that Sean Penn and Charlize Theron may be planning a wedding already.

Charlize Theron and Sean Penn kept things low profile while they were at the 86th Academy Awards, but they let rip soon aftter. Madonna was not spotted at the Academy Awards Ceremony, but her after- Oscar bash was the biggest party in Hollywood biggies in presence.

Madonna traditionally host an annual Oscars after-party. Last Sunday, Madge held hers at The Vineyard in Beverly Hills, Calif. which is owned by her manager Guy Oseary. The party rages on  from 10 p.m. until the early hours, breaking up around 6 a.m.. Madonna's ex-husband Sean Penn and his girlfriend, Charlize Theron wore matching outfits and hit the dance floor in front of A-Listers like Julia Roberts, Nicole Richie, Joel Madden, Brad Pitt, Angelina Jolie, Miley Cyrus, Tom Ford, Ellen DeGeneres, Portia De Rossi, John Travolta and Kelly Preston.

Witnesses told Us Weekly that Charlize and Sean were "making out like crazy" and "all over each other" on the dance floor. An insider said "They were the talk of the party - even Madonna noticed!"

Madonna's friend Debi Mazar said that Sean Penn is still Madonna's "one true love." Penn was supported his ex-wife at concert performances and she recently joined him in Haiti on a humanitarian project. Theron and Penn confirmed that they were a couple at a Haiti benefit.

"The couple is very much happening," a source revealed to HollywoodLife.com exclusively. "They were constantly close to each other and he was very protective of her at all times."

Charlize Theron and boyfriend Sean Penn also got hot at a pre-Oscars bash hosted by Oscar-nominated singer Pharrell Williams on Feb. 27.  at Eveleigh in Los Angeles.

Pharrell Williams Oscar bash was the first event Charlize Theron and Sean Penn attended together since early January when they went to Penn's Help Haiti Home Gala. Sean and Charlize were photographed holding hands, cuddling, dancing and kissing during the party.

One partygoer told Us Weekly "Watching Charlize and Sean get down! Both so hot. Charlize and Sean are so gorgeous together, a natural couple."

So, are there wedding bells in the future for Charlize Theron and Sean Penn? A source said "Sean is head over heels in love with Charlize, and her son Jackson. He is a totally different person around Charlize, she brings out the gentle and fun side that not many people have seen of Sean. To see this previously surly grown man, romping around Charlize's backyard with Jackson, with a smile on his face would amaze Sean's detractors. Charlize is getting Sean to not take himself too seriously."
The source said Sean and Charlize are already talking about getting married. Sean Penn and his ex-wife, Robin Wright, have two children, Dylan, 23, and Hopper, 20.

The source said Sean has expressed interest in adopting Jackson.

The insider continued "The two began talking about marriage in the last few weeks, after Sean moved into Charlize's house. She has never wanted to get married, but seeing how Sean interacts with Jackson, she is having a change of heart. For the longest time, Charlize thought it was just going to be her and Jackson, and she was OK with that. For her to now be talking about getting married is a huge departure for Charlize."