Diaz had a good sense of humor about the whole thing, but acknowledged that hooking up with an ex on-screen was a bizarre experience.
"Yes, yes. It was just [an] absurdity, a form of hilarity for all of us involved," she told PEOPLE. "We went to work that day and said, what time do we start being ridiculous? ... Eight o'clock? Perfect."
Katzen says the pair just brushed off the awkwardness and did their job with professionalism and lots of laughs.
"I guess the real truth is that they're good friends ... They're buddies," he said. "They got in there and started doing it. And it was so funny, we just couldn't stop shooting it. And we were doing it almost the whole day. And really crying, laughing at the [video] monitors."
Timberlake and Diaz dated from 2003 to 2007, but have both gone on to seriously date other people. Timberlake recently split from Jessica Biel, while Diaz has been dating New York Yankee Alex Rodriguez for about a year.
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