When Franco asks if he knows Conan O'Brien, Newall asks if he means Conan the Barbarian or New Zealand musician Connan Mockasin - which O'Brien mishears as "Conan Washington".
After the call, Franco explains that he has been answering the phone in character as Wiseau.
"We did our own billboard based on that, and it's my face, and we have a number and it goes right here. We've gotten over 200,000 calls.
"And you talk to these people yourself?", asks O'Brien. "As Tommy," confirms Franco.
In a blog post on flicks.co.nz, Newall explained how the bizarre phone call happened.
"As part of the promo for The Disaster Artist, the film a billboard went up in Hollywood mimicking the original set up to promote The Room," he wrote.
"I'd been trying to get through to Franco/Wiseau for weeks... I'd pretty much given up, and then in the middle of an Important Work Lunch I went to play my fellow diners the answerphone message, but something was different. Franco had picked up.
"And of all the times to get through to him… It was right at this moment."
On Twitter, he described it as "one of the strangest phone calls I've had in a while."
Mockasin later tweeted O'Brien with a reminder that he had once performed live on his show.
The Disaster Artist, based on the making of The Room, is currently screening in New Zealand.
