Best Friends! Jennifer Aniston's Maid of Honor Revealed

Courteney Cox did not just attend her friend's wedding.

"I'll be there for you like I've been there before."

The Friends theme song lyrics are definitely in our heads with the news that Courteney Cox was reportedly there as the maid of honor for longtime pal Jennifer Aniston at her wedding to Justin Theroux on Wednesday at the couple's Bel Air, California home, according to People.

What's more, a source told ET that Cox was also the last guest to leave.

Cox and Aniston have remained close friends since they first starred as Monica and Rachel on Friends in 1994. Aniston is the godmother to Cox's daughter Coco, 11, and Cox even got engaged to Snow Patrol's Johnny McDaid at Aniston's home last June.

WATCH: Inside Jennifer Aniston and Justin Theroux's Wedding: The Guests, the Secret Performance & More

In February, Aniston spoke about their friendship to More magazine. "She's extremely fair, ridiculously loyal and fiercely loving," the 46-year-old actress said. "She's been there for me through thick and thin."

As for Theroux's best man, he reportedly chose his friend Scott Campbell, a tattoo artist and husband of actress Lake Bell. Pal Jimmy Kimmel was also part of the festivities as he reportedly threw The Leftovers star his Bachelor party on Monday at a barn Kimmel built next to his house.

MORE: 9 Times Jennifer Aniston Gushed About New Husband Justin Theroux 

ET learned that the bride and groom's A-list guests included Tobey Maguire, Ellen DeGeneres, Portia de Rossi, Jimmy Kimmel, Howard Stern, John Krasinski, Emily Blunt, Jason Bateman, Will Arnett, Billy Crudup, and photographer Terry Richardson.

And of course Friends costar Lisa Kudrow was in attendance as well, which made us all wonder if they had a moment like this one!

A source told ET that guests danced to Michael Jackson, P. Diddy, Rihanna and Jay Z, and since the wedding was disguised as a birthday party for Theroux, who turns 44 on Aug.10, they also sang "Happy Birthday" to him around 10 p.m.

After the ceremony, the newlyweds boarded a private jet in Van Nuys, California, for their romantic honeymoon to Bora Bora.

Watch the video below to see more about the secret wedding.