Christian Slater is going to be a groom!During an appearance on Late Night With Jimmy Fallon on Feb. 27, The Robin Hood: Prince of Thieves star revealed he got engaged to his longtime girlfriend, Brittany Lopez.After confirming the joyous news, he went into detail about his first encounter with the young brunette. "I went down to Miami a couple years ago, stayed at this little place (resort) called Little Palm Island... and this girl came walking along with another lady, a slightly older lady," he said. "I was sitting in my usual spot, eating my oatmeal that morning... and this spot was famous for people proposing to each other... and next thing I know she gets down on one knee and proposes to this older lady..."He continues, "I thought I had just witnessed a nice lesbian engagement, so I was coming over to say congratulations, but it turns out it was her aunt and she was just trying to help her aunt capture the beauty and the romance of the moment. She was making a joke, and I witnessed it, and it intrigued me, and the next thing I know we were hanging out in the Everglades."And little did she know, years later, he'd pop that very same question!This will be the 43-year-old actor's second marriage. In 2000, he married journalist Ryan Haddon, with whom he has two children: Jaden, 13, and Eliana, 11. The pair separated in 2005 and divorced in 2007.