"Traveller," he said, "Traveller's a beer you travel with right?"
Karl Stefanovic immediately burst into laughter with Richard Wilkins telling the movie star, "You're not supposed to say that".
A confused Dempsey asked, "What's a traveller? Have I just alienated everyone in the country?"
With Stefanovic still chuckling in the background, Wilkinson said, "All the blokes who are watching are sitting upright now".
The topic came up, so to speak, later in the interview when Dempsey again asked, "What the heck is a traveller?"
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Wilkins leaned over to the star and whispered the answer in his ear.
For those who aren't aware, "traveller" is a term used to describe an erection that develops while on public transport.
After being educated by Wilkins, a clearly embarrassed Dempsey said, "Oh, excuse me".
Bridget Jones's Baby is in cinemas September 15.