Lady Gaga performed a 'Smelly Cat' duet with Lisa Kudrow on the 'Friends' reunion special

• HBO Max released the highly anticipated "Friends" reunion special featuring the six main stars.
• Lady Gaga made an appearance and performed the song "Smelly Cat" with Lisa Kudrow.
• Gaga also thanked Kudrow for playing a character who was "the one that was really herself."

HBO Max's "Friends" reunion special delivered on plenty of nostalgia, juicy revelations, and a performance of Lisa Kudrow's fan-favorite song "Smelly Cat" - with additional vocals by special guest Lady Gaga.

The unscripted special, titled "Friends: The Reunion," was released on Thursday and hosted by James Corden. Main cast members Kudrow (Phoebe Buffay), Jennifer Aniston (Rachel Green), David Schwimmer (Ross Geller), Courteney Cox (Monica Geller), Matthew Perry (Chandler Bing), and Matt LeBlanc (Joey Tribbiani) reminisced about starring on the 10-season sitcom and did table reads of iconic scenes.

The special also included appearances from other cast members (like Janice actress Maggie Wheeler) and celebrities who are fans of the show.

About an hour into the special, Kudrow began playing "Smelly Cat" on a guitar and singing while sitting inside the iconic Central Perk set. She was interrupted by Lady Gaga, who walked in the door with her own guitar.

"I love 'Smelly Cat,'" the Grammy-winning singer said. "It's one of my favorite songs."

Gaga performed the chorus before she and Kudrow teamed up for a duet of the track, which was first performed by Phoebe during season two, episode six.

Similar to how a chorus joined Phoebe while she recorded "Smelly Cat" later on the season, a group of singers popped up on the reunion special to sing with Kudrow and Gaga.

After singing together, Gaga spoke about relating to Kudrow's quirky character.

"Thank you so much for being the person for all of us on 'Friends' that was the, I don't think if this is the right way to say it, but the different one or the one that was really herself," the singer said.

In an interview with Variety, Ben Winston, the director and producer of "Friends: The Reunion," gave some insight into how the duet came together.

Winston said that Kudrow was open to playing "Smelly Cat" and they both agreed that having Gaga join "would be the ultimate one because she associates with and feels close to Phoebe in so many ways." They also pulled off the performance with little rehearsal time.

"That was a really beautiful moment," Winston said. "And Lady Gaga jumped at the chance to do it."

Head over to HBO Max to watch the complete performance and full "Friends" reunion special.