Tonight, only ET's Mary Hart is with Tom Cruise and Cameron Diaz on the top-secret Boston set of their new action-comedy, 'Knight & Day' -- and we have a sneak peek at their sit-down!

After letting loose in last year's 'Tropic Thunder,' Tom shows off more of his comedic chops in 'Knight & Day,' and Cameron reports, "He's so funny!"

As for the overall feel of the film, she clarifies, "It's not like a wacky comedy; the situations are kind of absurd."

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