It turns out Jennifer Aniston doesn't know Reese Witherspoon as well as she thought.

The Morning Show costars and friends of nearly three decades both learned something new about each other in a recent interview with LADbible, as Aniston, 56, was left dumbfounded after learning that Reese is not actually Witherspoon's name.

Witherspoon, 49, asked her costar to pick which of three names -- Jane, Jeanne or Joan -- was her middle name, and when Aniston guessed incorrectly, the Legally Blonde star said, "It's Jeanne. That's confusing. I'm Laura Jeanne."

"Laura Jeanne?" Aniston repeated back to her, confused, and Witherspoon confirmed, "That's my real name."

"Who's Laura? Who the hell's Laura?" Aniston said as the shocking news sunk in. "Wait, Laura Jeanne? I'm not calling you that from now on! Come on, Laura Jean."

She then asked, "Where did Reese come from?" and Witherspoon revealed it's her middle name.

Witherspoon said she "didn't change" her name when she went into the acting world, she was "always Reese."

It was then Aniston's turn to quiz her costar, who also didn't know what her middle name was. "Joanna," Aniston revealed.

"Jennifer Joanna," Witherspoon repeated. "J.J. -- Does anybody call you J.J.? Well I do now."

The actresses first met when Witherspoon starred as Aniston's younger sister on an episode of Friends in 2000. Witherspoon was just 23 at the time, and had just welcomed her daughter Ava with her then-husband Ryan Phillippe.

"Being on Friends, still to this day, is one of my scariest moments ever, because it was in front of a live audience, and I had never really done theater. I'd never been in front of a live audience," she previously told PEOPLE. "Jen was just the sweetest to me."

"I'd just had a baby, and I remember her and Courteney [Cox] running to my dressing room going, 'Can we see the baby?' 'You have a baby?' I was like, 'I do y'all, I have a baby.' They were like, 'Can we hold the baby?'"

Witherspoon remembered the "natural rapport and rhythm" that Aniston, Cox and their castmates Matt LeBlanc, David Schwimmer, Lisa Kudrow and the late Matthew Perry had.

"It was just these six people working in rhythm together," she said.. "You could tell they truly loved each other. It's really lovely to me, that I got to see them."