Actress Lindsay Lohan addresses reporters during a news conference at the 2014 Sundance Film Festival on January 20, 2014 in Park City, Utah. Producer Randall Emmett and Lohan announced the forthcoming production of a new film, 'Inconceivable', which Lohan will star in and co-produce.

London - Lindsay Lohan wept as Oprah Winfrey praised her on David Letterman's show on Thursday night.

The 'Mean Girls' actress - whose post-rehab attempts to get her career back on track are being chronicled in documentary series 'Lindsay' on the media mogul's OWN network - initially planned to prank call her mentor, but the retiring talk show host quickly blew his own cover and had a serious chat about his famous guest instead.

Lindsay asked the audience: "I think maybe I should just call her right now. Should we call Oprah?

"I think so. Do you have a phone? Have we got a phone?"

Letterman, 66, took the phone and in a feminine voice said: "Yes, can I speak to Oprah Winfrey please? Hi, this is, uh, Lindsay Lohan's secretary."

He quickly owned up to his real identity when Oprah asked who was on the line, prompting her to reply: "Very good, Dave! The David Letterman who's retiring?!"

Getting the conversation back on a serious track, the talk show host asked: "How's our friend Lindsay doing?"

Oprah then spoke of her pride in the 27-year-old star's attempts to turn her life around.

She replied: "I think she's doing OK ... What do you think? ... I think she's doing really OK. I think to have cameras following you around for every phase of your life and you're trying to pull your life together, I think that's a really difficult thing. We're really pleased that she's making some progress."

Lindsay - who has been in rehab six times - then wiped away tears. - Bang Showbiz