Perry and Cox played husband and wife Chandler Bing and Monica Geller on the long-running NBC sitcom.
The 59-year-old Scream actress took to Instagram on Tuesday to share a scene from the series that features their characters -- Chandler Bing and Monica Geller -- getting together for the very first time. In the post, she shared a little behind-the-scenes knowledge on how their fan-favorite storyline also came together after what was originally supposed to be a one-time thing.
"When you work with someone as closely as I did with Matthew, there are thousands of moments I wish I could share. For now here's one of my favorites," Cox wrote.
"To give a little backstory, Chandler and Monica were supposed to have a one night fling in London. But because of the audience's reaction, it became the beginning of their love story," she continued.
"In this scene, before we started rolling, he whispered a funny line for me to say. He often did things like that," Cox wrote.
The scene features Cox's character hiding underneath a blanket in bed with Perry's character in an effort to hide their hookup. Monica eventually pops up from underneath to ask if Ross -- played by David Schwimmer -- knew that she was there and therefore romantically involved with Chandler.
The video Cox posted also features a behind-the-scenes clip of what happens after they cut, including her telling Perry to go under the blanket as it was "his turn."
"He told me to say that, he really did," a young Cox says in the snippet.
"He was funny and he was kind," the actress shared with her 15 million Instagram followers. "I am so grateful for every moment I had with you Matty and I miss you every day."
Cox's post comes just hours after another one of Perry's Friends co-stars shared a message to the late actor.
Early Tuesday morning, Matt LeBlanc -- who played Joey Tribbiani -- also took to Instagram and posted a carousel of photos from scenes they shared on the popular sitcom, including from season 2's "The One After the Super Bowl, Part 1" and season 4's "Joey and Chandler Get Robbed."
"It is with a heavy heart I say goodbye. The times we had together are honestly among the favorite times of my life," LeBlanc, 56, wrote in his caption. "It was an honor to share the stage with you and to call you my friend. I will always smile when I think of you and I'll never forget you. Never."
At the time, the actors joined the world in mourning Perry's death and thanking him for his years of hard work and friendship.
"We are all so utterly devastated by the loss of Matthew. We were more than just cast mates. We are a family," their statement shared. "There is so much to say, but right now we’re going to take a moment to grieve and process this unfathomable loss."
"In time we will say more, as and when we are able," the statement continued. "For now, our thoughts and our love are with Matty’s family, his friends, and everyone who loved him around the world.
The entire cast also attended Perry's funeral on Nov. 3. ET learned that the beloved actor was laid to rest at Forest Lawn Memorial Park in Los Angeles, not far from Warner Bros. Studios where he filmed Friends.