Appearing on the US show to promote his latest movie, Die Hard 4.0, Willis was on top form acting up as a born again environmentalist.

And the man behind All American hero John McLean explained to a stunned host that he’d gone ”off grid” with his latest invention.

“In fact, I can’t even see the grid anymore”, he said.

With the audience not sure whether to laugh or call the men in white coats, Willis then announced he’s working on a new documentary to rival Al Gore’s An Inconvenient Truth.

“It’s a working title. I think I’m going to call it, An Unappealing Hunch,” he said.

“This whole global warming thing — I’m not convinced. I’m a little sceptical,” he continued. “I’m thinking that the problem isn’t global warming, but ‘global humidity’. Have you been outside today folks? It’s unbelievable. Right now, I’m wearing a pair of boxer briefs made out of recycled tyres. A little chaffing problem, I’m not going to kid you…”

But don’t think the man’s making fun of being green for the sake of it. Despite his penchant for explosives and track record as a Republican campaigner, Willis is in fact a committed environmentalist – and is even looking to buy himself an electric car.

“I live in Los Angeles and spend about five hours a day in a car,” Willis said, speaking to press last year. “I know a lot of people who used to own those big cars but are changing over. I’m getting an electric car because it makes sense to use an alternative to digging up oil.”

Watch the full interview here

Die Hard 4.0 is released on 4th July