"I was really nervous when I first heard that," Kudrow says of learning that she'd be singing with Lady Gaga. "Then I prepared. I realized I had to learn 'Smelly Cat' again. I tuned my guitar and realized I don't know the chords. But I Googled it! All the chords were there. Thank you, world, for posting the chords. So I learned it." After re-learning the chords to the song, Kudrow still had trouble performing it in the moment. "And then, my throat closed. I was so panicked. I couldn't get anything out. I didn't know what was going to happen," said. "But it worked out." ALSO: David Schwimmer shares behind-the-scenes pics, including a Zoom photo of the Friends cast preparing for the reunion.