AceShowbiz -

Joaquin Phoenix announced his engagement on "Late Show with David Letterman" on Monday, December 8. He told David Letterman he fell in love with his yoga instructor girlfriend after attempting a position called "harnessing the hog."

The star of "The Master" recalled his first meeting with his yoga instructor. "First we do these breathing exercises and I go, 'I can do this,' " he told David, "And then she says we are going to get in the first position - the 'harnessing of the hog.' They have like all these weird animal names." The 67-year-old host then responded, "That's a carnival ride, that's not yoga."

Joaquin then left his seat to demonstrate the position to the audiences. "Before I can say, 'Who is the hog?' She grabs me... and it's a compromising and vulnerable position... She gets a strap and puts it [around me] and she's thrusting [against] me and I go, 'Oh, no! My back pain!' And she goes, 'No, that's your emotional back pain.' "

After returning to his seat, the "Walk the Line" actor told David, "This is the crazy part of the story. We started dating, and I think she's the one. I proposed to her and she said yes." David then asked him, "You proposed to her? So you're getting married?" to which he replied, "Well, I mean if everything works out."

Joaquin can be seen in upcoming movie "Inherent Vice" along with Josh Brolin, Reese Witherspoon, Benicio Del Toro and Owen Wilson. The crime comedy-drama flick is set to hit U.S. theaters on December 12.