Since the first season, Carol Willick has been a consistently enjoyable character. Ben has been well raised by her, especially given that Geller doesn't seem to take him very frequently. 

Carol Willick

Early on in the episode, Pete Becker was shown as Monica's lover. He had a lot of money to spend, but he went above and beyond to win over the girl of his dreams.

Pete Becker

Another parental character in the programme is Alice. She also has a close friendship with Phoebe, a surrogate for Alice's brother Frank Jr.

Alice Knight Buffay

Friends contains a lot of selfish characters, who are often trying to get the best for themselves in the situations they are put in. Erica is one of the few selfless people in the show. 

Erica

Rachel's annoying sister showcased just how far the original Green has come in terms of her character progression. Amy was the complete antithesis of everyone Rachel was in the final seasons. 

Amy Green

David was a recurring love interest for Phoebe who showed up intermittently throughout the show. Until she eventually came back and was overtaken by Mike, he always seemed to be the one who escaped.

David

Tag is probably a forgettable character in the large scheme of things, but Rachel's former boyfriend was one of the most fun people that has ever been on the show. 

Tag Jone

Estelle was the best agent in the business. Sure she didn't have many clients and those she did have had peculiar talents to say the least.

Estelle Leonard

Charlie Wheeler

Charlie was a pretty perfect girlfriend for Ross. She was intelligent, funny, kind and actually got on well with many of his friends  

Early on in the episode, Pete Becker was shown as Monica's lover. He had a lot of money to spend, but he went above and beyond to win over the girl of his dreams.

Mr Zelner