Rachel. Ross. Monica. Chandler. Phoebe. Joey. Not many series have a cast of main characters that have become so iconic that they're recognizable by first name only. The long-running sitcom Friends, however, is not like most other series, standing the test of time as one of the most successful and beloved sitcoms to ever air.

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While it was the main characters of the series that drew people into watching Friends for the long term, there's no denying that there's much more to the series than its core cast of Central Perk regulars. Friends has a truly colorful and distinct universe, filled with vibrant characters used in hilarious and touching ways. Here, we recap some of the most underrated supporting players in the series.

The Chick and the Duck

The duck and the chick with Joey and Chandler

Chandler and Joey, needless to say, develop a bromance for the ages over the course of the series. But one of the best things to come from their time as roommates is, without question, the introduction of two pint-sized, fluffy characters.

The chick and the duck do not speak, of course, or have any real characterizations of their own. But somehow, over the few seasons in which they appear, they develop their own personalities and personas, acting as the odd couple's quasi-children and getting into plenty of mischief along the way.

Erica

Friends more or less perfected the character archetype of the airhead with a heart of gold in its main characters Joey Tribbiani and Phoebe Buffay. But in the series' final season, it once again proved why it was the best at handling this particular trope with the introduction of Anna Faris's Erica.

After it becomes clear that Chandler and Monica won't be able to have a child on their own, they look into both surrogacy and adoption, and eventually, they find Erica - a well-meaning but truly clueless young girl from Ohio. While not the brightest bulb, Erica brings a lot of heart and humor to the series in her brief arc.

Phoebe Abbott

Phoebe Buffay has the darkest backstory of any of the main characters, and the series delves into exploring it through darkly comic means. But one of the biggest surprises that came as a result of Phoebe's search for answers about herself was the introduction of Teri Garr's Phoebe Abbott.

At first, Phoebe Buffay believed that Phoebe Abbott was just a friend of her mother's, and her namesake. But as became quickly apparent, given their near identical personalities, Phoebe Abbott was in fact her birth mother. Thanks to Garr's nuanced and warmly quirky performance, Phoebe Abbott was always a joy to behold in the few appearances she made in the series.

David

Hank Azaria as David in Friends

Love interests are more or less a dime a dozen on Friends, considering the fact that the series follows a group of twentysomethings trying to find success and love in the real world. But while many love interests wouldn't prove to be "the one" for their respective significant other, some of them certainly could have been a totally valid choice. And some of them came quite close to getting the happily ever after.

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None of them came closer than Hank Azaria's David, the quirky scientist that fell in love with Phoebe early in the series' run. In the later seasons, David returned, sweeping Phoebe off her feet once again, and even planning to propose to her. Thanks to Azaria's distinct line deliveries, David routinely proved why he was such a good match for the likewise zany Phoebe, even if they didn't end up together.

Mr. Heckles

Mr Heckles in Friends

Since the gang of main characters are living in densely populated apartment buildings in New York City, it was inevitable that they would run into some colorful characters in these places. Far and away one of the most enjoyable of them, albeit totally underutilized, was the bizarre neighbor Mr. Heckles. His name made sense, considering how often he harangued and heckled the friends for their behavior and noisiness.

More than just a typical crotchety old man, Heckles always seemed just a little bit off, almost like Friends' elderly version of Seinfeld's Kramer. He seemed to live in his own world, didn't rely on typical social conventions, and always wanted things just his way - even if that meant stealing a monkey or two.

Jack Geller

Elliott Gould as Jack Geller in Friends

There aren't many particularly gifted parents in the world of Friends. Basically all of the main characters have fractured relationships with their parents, and whenever their parents come into town, you can guarantee it will lead to conflict. But far and away the best parent introduced in the series is Ross and Monica's father, Jack Geller.

While not always the most astute or aware, Jack routinely proves that he is a good man, with a keen sense of humor. He is fiercely protective of both of his children (though his little Harmonica often complains that Ross is the favorite), and he wears his heart on his sleeve, for better or worse. Elliott Gould brings Jack's character to life in a beautiful way that is at once hilarious and heart-warming.

Richard Burke

David isn't the only runner-up love interest who stands out as one of the series' best supporting characters. Despite the considerable age difference between them, and all the judgment and obstacles that stood in their way, the relationship between Monica and Tom Selleck's Dr. Richard Burke remains one of the series' most emotionally compelling storylines.

Richard is never quite welcomed into the series' main group of friends, the generational difference leaving him an outsider in more ways than one. But Selleck's portrayal of Richard is winningly warm and deeply romantic all at the same time. It's not hard to understand why Monica falls for him time and again, and why Richard never really got over her, either.

Mike Hannigan

Paul Rudd as Mike Hannigan in Friends

It was only natural that Phoebe would meet her soulmate through less-than-conventional means. Mike Hannigan, portrayed by the eternally lovable Paul Rudd, was a total stranger that Joey portrayed as his friend when trying to set Phoebe up on a date. It shouldn't have made sense for the two of them to hit it off the way they did, given all the lies that went into creating their introduction in the first place.

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But thanks in large part to Rudd's charm and total commitment to all forms of humor, Mike remains one of the series' most successfully executed characters, responsible for some of Friends' most hilarious and heart-warming moments. It's a shame, really, that the series waited so long to introduce him, as he only appears in less than a season's worth of episodes.

Frank Buffay Jr.

Frank Jr. celebrates Phoebe's pregnancy news

Phoebe Buffay has led quite the colorful life, and she's got the unconventional siblings to show for it. But while the series tried in vain to milk the Ursula plot for far more than it was worth, it finally succeeded with the introduction of her younger half-brother, Frank Buffay Jr.

Giovanni Ribisi gives a comedic tour de force performance in the role of Frank. He marries his much older home economics teacher, asks his sister to be a surrogate when his wife can't conceive, and returns as a sleep-addled man desperate enough to momentarily half-consider giving away one of his triplets. He's entirely over the top and entirely lovable all the same.

Marcel

Marcel Monkey Friends

As we've already seen in the case of Chandler and Joey's beloved chick and duck, characters don't have to be human to meaningfully contribute to a series as successful and beloved as Friends. But far beyond the hilarity those two little birds provided in their tenure on the series, Ross's beloved pet monkey, Marcel, changed the series for the better in many, many ways.

Some of Marcel's most memorable moments include his penchant for playing "The Lion Sleeps Tonight" on loop and the time when he grasped Ross's finger and made him realize just what it meant to be a father. While Marcel couldn't conceivably stay on the series for very long, given the amount of trouble he caused, there's no denying that he left quite the fuzzy little hole in everyone's hearts.

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