In advance of her guest spot on next Monday’s 2 Broke Girls, Lindsay Lohan dropped by The Late Show, where discussion quickly shifted to LiLo’s “mentor”; and Dave’s foe-turned-pal Oprah Winfrey, who’s also exec producer of Lindsay’s OWN talk show Lindsay.

“I think maybe I should just call her right now,” suggests Lindsay. “Should we call Oprah?”;

Dave does not seem to be a fan of the idea, insisting, “No, we’re not.”;

But Lindsay persists, encouraging the audience to chant “Op-rah! Op-rah! Op-rah!” until Dave finally relents. When he gets her on the line, however, he puts on a wispy fake voice, pretending to be “Lindsay Lohan’s secretary” until finally admitting, “It’s Dave, Oprah, it’s Dave.”;

“Oh my God,”; says Oprah with a laugh. “Very good, Dave! The David Letterman who’s retiring?”;

LINDSAY LOHAN REVEALS OPRAH IS A “GUIDING LIGHT’ IN HER LIFE

After discussing how instrumental Oprah has been in helping Lindsay get her troubled life together, Dave quips, “Oprah, I’ve spent 30 years trying to pull my life together — where the hell have you been?”;

Finally, Dave shares some personal spiritual news with Oprah: “You know what else, Oprah, that I’ve switched to now, that is really fantastic? Scientology,” he deadpans, leaving Oprah, Lindsay and the audience in stitches.

You can catch Lindsay’s entire interview on tonight’s edition of The Late Show With David Letterman.