The 52-year-old Friends star has been posting endless behind-the-scenes photos from the much-anticipated reunion, which aired on screens last week.
Many of the pictures are of the American actress and her co-stars, looking over the moon to see each other.
She shared: “Swipe for… The bazillionth selfie taken with the five of us… When two TOTALLY different worlds collide – @_schwim_’s face says it all… The legend himself, our director of the first season, Papa James Burrows.”
Some fans were left confused, however, when they noticed singer/songwriter Justin Bieber and his wife Hailey were on the set.
“Why is Bieber there? Lmao,” one person queried.
Another said: “I still don’t understand why Justin Bieber was there?”
“No reason for hailey and justin bieber to be there,” a third quipped.
However others defended the star, with one fan sharing: “Because he adores Friends! Him and Hailey watch it every single day. Justin has suffered with anxiety a lot and he has said that watching Friends has helped him a lot in those moments.
“He has loved the show for years and during the first year of his career he used the name Chandler Bing when booking hotel rooms.”
“To pull in a younger audience,” another commented.
And a third added: “Um because he was invited? Like other guests? Like David Beckham and Cara and everyone else? Why r u guys so pressed I just don’t get it.”
It appears fans of the star are right, as he previously went undercover to surprise Friends lovers during an appearance on The Ellen Show.