The actress, 51, posted several snaps on her Instagram story as Lisa Kudrow turned 57 and revealed her nickname for her former co-star.
Delving back into the photo archives, Jennifer uploaded a variety of throwback shots, including a cheeky picture of the pair making faces to the camera.
The US star, who played Rachael Green on NBC's Friends, was a late arrival to the photo-sharing app opening an account last year but wasted no time in sharing images about her life on the platform.
Adding another picture, Jen declared "I love you" along with a pic of her cuddling Lisa at an awards ceremony.
She wrote: "Happy birthday my sweetest Floosh," before adding a video of Lisa joining Taylor Swift on-stage in 2015, singing a rendition of "Smelly Cat" that was first heard when her character Phoebe Buffay wrote the iconic tune on Friends.
Jen, Lisa and Courtney Cox recently reunited for a social media video urging people to vote in the November elections.
The 'I Am a Voter' campaign saw the trio appearing in a short clip called "Friends don't let friends skip elections".
And the trio, along with the other Friends cast were hoping to reunite for a highly-anticipated reunion episode – but the show had to be postponed due to the global pandemic.
After the hit show wrapped in 2004, following ten years on air, fans have been begging the cast to get back together – and people's dreams became a reality when the co-creators announced they're getting back the stars for an unscripted special.
The episode is set to be filmed in the illustrious Burbank studios – the same place Friends was filmed.
With the global pandemic still taking hold, Lisa recently revealed they've penned in August as a could-be date for production.
Speaking to Conan O'Brien, she explained: "We have something on the books for us to do at some point in August.
"We are all still waiting for guidelines in terms of shooting things."