TOM Cruise had no idea you could watch pornography on the internet until Seth Rogen told him.

Writer and director Judd Apatow was there to witness the moment Tom Cruise learnt about porn and told talk show host Stephen Colbert all about it on The Late Show.

“I did once have a meeting with Tom Cruise,” Apatow said. “He’s a very, very nice man.

“I got asked to meet him. He was looking potentially to do not an action movie, a romantic comedy.”

This was back in 2006 when Apatow was making Knocked Up with Seth Rogen and he invited the actor to join him for the meeting with Cruise.

“No one knew who Seth was,” Apatow recalled.

“He wasn’t famous so he was just a dude with me and so I said, ‘Someone needs to witness this.’

“So we’re talking to him (Cruise), and I don’t know how it came up, but it usually comes up with Seth where (he) starts talking about marijuana and pornography.

“And he starts talking about watching adult films on the internet and Tom Cruise goes, ‘What? You’re saying there’s adult films on the internet?’

“And Seth’s like, ‘Yeah, there’s all these movies on these websites.’ And Tom Cruise’s like, ‘Wait a second. You’re saying if I go on the computer, on the world wide web, there are people having sex?’”

Rogen told Cruise that he watches porn on the internet “all the time”.

“Everybody does it, it’s not a big deal anymore,’” Rogen said, according to Apatow.

The Knocked Up director told Colbert he still isn’t 100 per cent certain if Cruise was actually hearing about internet porn for the first time.

“He was being very polite, but I think … I assume he was against it and being polite, but who knows,” Apatow said. “We’ll never know.”