"I’ll just be over here with my sexual charisma," the 37-year-old Brand joked to the Smash stunner, who said, "Oh my gosh … this is just too much for the first 30 seconds!"
The lanky comic added, "I find Katharine very attractive … I thought of things that I’d like to exchange with her … genetic info, data."
After the 28-year-old actress finally told the Get Him To The Greek star she was married (to producer Nick Cokas), he dropped a few lines before making his way off the stage.
"You could drop that guy any day … turn and face the change, ch-ch-ch-ch-changes … I didn't know you were married -- I'm gonna f*** off now," he said, walking off the show.
McPhee took the Brand's aggressive advances in stride, tweeting afterwards, "That was soooo much fun! And a little crazy too. Thank you for having me!"
Watch the video on RadarOnline.com
The new season of McPhee's show Smash premieres Tuesday 9/8c EST on NBC.