Jennifer Aniston and Lisa Kudrow have been good pals since they met on the set of Friends back in 1995, and now Jennifer has taken to Instagram to wish a happy birthday to "one of my favourite people on the planet," while also revealing the unusual nickname she has for her former co-star.

Jennifer posted a handful of pics of her and Lisa from over the years to pay tribute on her 60th birthday.

The first snap was seemingly from their joint Got Milk commercial photoshoot, where the Friends alums both posed with milk on their upper lip.

Another pic showed the two cuddling up to one another on a couch as they both looked baby-faced.

Other photos included one with their fellow Friends co-star Courtney Cox and another with all of the main Friends cast members.

READ MORE: Friends' Lisa Kudrow looks flawless as she celebrates her 60th birthday

The actress began her sweet message to Lisa by writing: "Please join me in celebrating one of my favorite people on the planet. LISA KUDROW!!" followed by a balloon emoji and smiley face emoji with a party hat on.

She continued the post, adding: "She's been my friend and my family for nearly 30 incredible years.

"One of the most talented comedians/actors I've had the great honor to work with for all these glorious years and more to come! Happy Lisa's Birthday!"

It's unclear where the nickname "Floosh" originated from, but it's clear the pair still share an unbreakable bond.

And it appears Lisa has her own adorable nickname for Jennifer too.

Under the Marley & Me star's birthday post, Lisa commented: "My Joooiest Joooo I love you beyond my dear friend forever!"

Lisa turned 60 years old on July 30 and celebrated her special day with a chocolate cake, according to her Instagram.

The Friends actress posted a photo of her on her Instagram Story as she sat at a table with a cake in front of her with candles that marked her age.

She captioned the post: "Thanks for all the happy birthday wishes. This wish is for all of you!"

Lisa, who played Phoebe, and Jennifer who played Rachel were two of the six main characters on the beloved 90s sitcom that originally aired on NBC.

The comedy series went on to be a huge success and ran from 1994 to 2004 and revolved around six friends played by the aforementioned Jennifer, Lisa, and Courtney along with David Schwimmer (who played Ross Geller, Matthew Perry (Chandler Bing), and Matt LeBlanc (Joey Tribbiani).

The show kickstarted all of the young actors' careers and they all attended a reunion special episode that aired on HBO Max in 2021, 17 years after the last episode aired.