The first two seasons were mostly centered on the on-off saga of Ross and Rachel, and while their relationship remained a strong presence through romantic rivals and even a baby, the other characters eventually moved from sideshow players into a shared comedic lead. But Friends was not without its heart. Most of the cast had dysfunctional relationships with their parents and went through loss, divorce, marriage, parenthood, and love triangles. The emotional pregnancies of Rachel (by Ross) and Phoebe (surrogate to her half-brother's triplets) won the actresses Emmy Awards, and Joey's tender feelings for Rachel in Season 8 won LeBlanc, the most improved actor in the series, a nomination.

Most sitcoms run out of ideas by the fifth season, but Friends gave itself a refreshing jolt the minute Monica and Chandler wound up in bed together. Their budding romance was not only the one of the funniest arcs of the series, but one of the most sentimental, as they planned a wedding, struggled to have a child and eventually turned to adoption. By seasons seven and onwards, the characters had each "grown up" from young singletons to thirtysomethings finding permanence in their careers and love lives but never losing the laughs.

Friends featured a parade of celebrity guests, but utilised most of the stars as more than mere cameos: The sextet's parents were all brilliantly cast, particularly Kathleen Turner as Chandler's drag-queen father and Teri Garr as Phoebe's dizzy mom. Everyone from George Clooney to Sean Penn to Julia Roberts to Bruce Willis has appeared on the sitcom, and Tom Selleck certainly enjoyed a career resuscitation after his recurring role as Monica's older man.