The two had a mini Friends reunion in West Hollywood, California, on Friday, teaming up for Burn 60's First Responder Studio Challenge, "Burn to Remember," which paid tribute to fallen first responders. ET spoke with the co-stars turned pals at the event, where they opened up about their ongoing friendship with the tight-knit cast, supporting each other for decades and how they became involved with the cause.
Kudrow, 54, and Cox, 53, arrived separately to the fitness studio, but immediately found each other once inside. They were all smiles while posing together on the red carpet, rocking matching gray "Burn Sixty" pullovers.
"We actually signed up so we could do this together," Cox said. "Well, that's what I did!"
"Yes, we both knew that we were going to be here today," added Kudrow, who also talked about how "great" it is to have each other's support all these years. "I mean, anyone who has friends for a long time I think can relate. Courteney's shown up for everything. Everything!"
Cox agreed, telling ET, "It's true."
"I know that whatever I have to do in life, if there's something that I signed on [to], I know that she'll be my first call," Cox added. "And she'll go."
And when they're not physically together, the close pals keep in touch with a Friends text chain they have going with Jennifer Aniston.
"Oh, yeah, we have one," Kudrow shared. "The girls do. There has been one [with the full cast] from time to time, trying to work out a dinner. But that's a lot of pressure."
We then turned the conversation to fitness, explaining that it looked like the workout they were about to take part in was pretty "intense."
"Well, luckily there'll be a lot of first responders in there," joked Kudrow, as Cox revealed they're "just trying to get by."
Inside the class, Kudrow and Cox seemed to be having a blast, chatting amongst themselves while walking on the treadmill alongside Zeus, a first responder canine, as songs like Bruno Mars' "Finesse," Missy Elliott's "Work It" and Kanye West's "Stronger" played through the speakers.
Both ladies told ET that they first heard about the event from their mutual friend, Janet Crown, who co-founded Burn 60 studios with her husband, Steve Robinson.
"We know Janet really well," Kudrow explained. "Like, for 20 years! But first responders, they run toward danger, so everyone else can get out of it. That's, for me, No. 1 [why I'm here]."
Cox chimed in, saying, "This is to raise awareness and funds for the fallen first responders. We really want to help out the families."
ET also spoke with Crown, who told us that 133 first responders and 93 firefighters lost their lives in the line of duty just in the past year. The event was put on to help raise money for Run to Remember, a half marathon that's taking place April 8 at The Grove in Los Angeles.
"These wonderful women are here to help us support and raise funds," Crown said. "To give back to those fallen first responders and their families."