Meg Ryan and Billy Crystal in the classic deli scene from 1989's "When Harry Met Sally."

Rob Reiner is opening up about a casting regret at the center of one of his most famous scenes.

The celebrated director, 78, who helped shepherd '80s rom-com "When Harry Met Sally…" to cult classic status, revealed in a new interview with "60 Minutes" that putting his mother in one of the film's central scenes ended up being incredibly awkward.

In it, Meg Ryan, who costars in the film with Billy Crystal, simulates an orgasm over a lunch of sandwiches at Katz's Delicatessen, screaming and banging on the table to prove to Crystal's character just how real it can sound. The scene wraps with Estelle Reiner, the director's mother, who is sitting nearby, telling the waiter: "I'll have what she's having."

"First couple of times, she didn't do it full out," Reiner told "60 Minutes" of directing Ryan in the now-famous scene. "Finally, I sat across from Billy. And I acted it for her. … And I'm pounding the table, 'Yes! Yes! Yes!' And I'm realizing I'm having an orgasm in front of my mother, you know? There's my mother over there."

Estelle Reiner, who died in 2008, was both an actress and a singer, performing in cabaret shows for several decades. Despite an illustrious and lengthy career, her brief utterance in "When Harry Met Sally" remains the most famed moment of her career, ranking among the most notable one-liners in the pantheon of American film.

This article originally appeared on USA TODAY: Rob Reiner knows you love his mom in 'When Harry Met Sally,' but he has mixed feelings

Reporting by Anna Kaufman, USA TODAY / USA TODAY

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