Unexpected, mismatched couple alert!

Witnesses spotted Gerard Butler and Ashley Greene getting both hot and heavy on June 7 at the Boom Boom Room in New York City.

"He had a hand on her shoulder and leaned in to her," a source told Us Weekly. "He really turned on the charm."

Greene was most recently linked to Joe Jonas, while Butler fought off Lindsay Lohan over the weekend.

But he went the other way with this Twilight beauty. He reportedly sang along with Journey's "Don't Stop Believing" and then, insiders swear, the Scottish actor put a hand on her butt. Oh, yes. This sounds serious.

[Photos: WENN.com]