Airing from 1993 to 2004, NBC's Frasier was one of the last truly great sitcoms of the golden era of comedy television. With a stellar cast boasting the likes of Kelsey Grammer, David Hyde Pierce, Jane Leeves, Peri Gilpin, and the late John Mahoney, the series was always witty, always intelligent, and always hilarious. It never leaned too heavily into stereotypes, or catered exclusively to a high brow or low brow audience, despite the snobbiness of its central characters. Frasier was a perfectly balanced sitcom, and that's why it continues to stand the test of time after all these years.

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While the series had one of the strongest core casts of a sitcom in recent memory, it also excelled in another key area as well: guest stars. No matter the level of significance of the guest star in terms of the length of their run on the series, Frasier always delivered in terms of finding the best and brightest to add to its already impressive ranks. Here, we take a look back at the ten best guest stars the series had to offer, and reflect on just what it was that made them so great.

Anthony LaPaglia (Simon Moon)

Anthony LaPaglia as Simon Moon in Frasier

Over the course of the series, Frasier began to explore more of the kooky, albeit caricature-like family of the beloved Daphne Moon. For the most part, these additions were a real mistake, and subtracted from the series as a whole. But in the midst of the cringe-worthy storylines and one-note characterizations, Frasier struck comedy gold with the casting of Anthony LaPaglia as Daphne's lout of a brother (one of many she has), Simon.

Simon is a totally classless character, spending most of his time drinking and sleeping around, which leads to hilarious points of conflict with not only Daphne, but the much more uptight Niles and Frasier. Even Roz can't stand him in the end, despite some of their fundamental similarities. A little bit of Simon goes a long way, but LaPaglia's work as the total oaf makes that little bit mean a whole lot.

Tony Goldwyn (Roger)

Tony Goldwyn as Roger in Frasier

For almost the entire series, Roz Doyle was a fiercely independent and openly sexual woman who never found a man who moved her in any meaningful way. All of that changed with the ninth season episode "Love Stinks," and the introduction of Tony Goldwyn's Roger. Roger was a garbage truck worker, and his difference in status and career from Roz and her higher-class friends made her initially uncomfortable.

But during all of the scenes they shared together, Roger, through Goldwyn's nuanced performance, radiated warmth and compassion, especially when it came to playing with little Alice Doyle. He and Roz made such a lasting impact in their one episode on screen together, that Roger would continue on with the series for a while as Roz's long-time boyfriend - although sadly remaining off screen.

Rita Wilson (Hester Crane and Mia Preston)

Rita Wilson and Kelsey Grammer in Frasier

It was only a matter of time before a psychotherapy-focused sitcom like Frasier took things to uncomfortably Freudian levels. Rita Wilson had a truly unenviable task on her hands when she guest starred on the series in a dual role. But in every way imaginable, she knocked it out of the park, appearing not only as Frasier's latest lady, Mia Preston, but his mother and her exact doppelganger, Hester Crane, in flashbacks.

While it's clear that nothing can become of Frasier and Mia's relationship due to the uncomfortable Oedipal reveal, Wilson does most of her best work in the series in her role as Hester Crane. Hester appears twice with Wilson's portrayal, once in home movies and another in a downward spiral of Frasier's psyche, and every time, Wilson's Crane matriarch is every bit as warm and formidable as anyone could expect.

Irene Olga López (Marta)

Irene Olga Lopez as Marta in Frasier

Frasier fares only slightly better than its contemporary Friends in the category of diverse casting, but arguably one of its most important characters of a diverse background is Marta, Niles and Maris's maid, who is fiercely loyal to the mysterious Maris from day one. Appearing in only a handful of episodes, Marta nevertheless makes quite the impact, and it's all thanks to the impeccable comedic timing and performance of Irene Olga López.

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Most of the humor that Marta adds to the series stems from her poor level of English understanding, and her tendency to switch pronouns and genders, such as when she refers to Niles as "Missy Crane." But López's strength of screen presence, and her dry line delivery, elevate what could be an offensive stereotype into true comedic gold.

Wendie Malick (Ronee Lawrence)

Wendie Malick and John Mahoney in Frasier

Just as Niles and Frasier go through their fair share of love interests over the course of the series, so, too, does Crane patriarch Martin. But it's not until he reconnects with a woman from the Crane family's past that he finds a real winner. Ronee Lawrence was once Niles and Frasier's babysitter when they were young and not so troublemaking, and she made quite an impression on the siblings. In the end, though, it's the elder Crane who wins her heart - and it's thanks to the inimitable Wendie Malick that Ronee wins the audience's hearts, too.

The introduction of Ronee adds yet another welcome female voice to the series, and from the very beginning, it's clear that she can hold her own against all of the Crane men, thanks in large part to Malick's strength of screen presence. Ronee and Martin feel like a totally natural fit for one another, despite their considerable age difference and unconventional background, making Ronee's presence on the series ever-welcomed.

Victor Garber (Ferguson)

Victor Garber as Ferguson the butler in Frasier

It was inevitable that the dynamic of the Crane family would change fundamentally once Niles and Daphne began seeing one another, given Daphne's status as Martin's home care provider. In a first attempt at rectifying this new change in status quo, Frasier decided to hire a butler for the Crane family home, a wonderfully posh and stuffy fellow by the name of Ferguson played by none other than the legendary actor of stage and screen Victor Garber.

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Ferguson was perfectly suited for catering to each and every one of Frasier's high society needs, and Garber played each snooty comment and haughty pose to perfection. Ferguson even seemed to out-snob both Frasier and Niles, which brought the series a real first that it, sadly, only made use of for Garber's sole appearance.

Brian Stokes Mitchell (Cam Winston)

Frasier talking to his rival Cam Winston on Frasier

Frasier had his fair share of rivals and nemeses over the course of Frasier's eleven-season run, but none of them loom quite as large --or leave you in as many fits of hysterical laughter-- as Brian Stokes Mitchell's Cam Winston. A familiar face to fans of other comedies including The Fresh Prince of Bel-Air, or die-hard theatre fans, Mitchell's deep bass voice alone commands quite the impressive screen presence, and lends his character a level of seriousness that not even Grammer's esteemed Dr. Crane can command.

What makes Cam such a winning rival, however, is the fact that he and Frasier are virtually identical characters in terms of taste and levels of snobbiness. The series has great fun with their short-lived dynamic when Martin and Cam's mother engage in a romantic relationship with one another, forcing Frasier and Cam to reconcile with the very real possibility that they could become brothers-in-law. And all the while, Mitchell is a totally game performer, hamming it up every chance he gets.

Laura Linney (Charlotte Connor)

Laura Linney as Charlotte Connor in Frasier

Frasier Crane romanced his fair share of women over the course of Frasier's run, and even including his mercurial ex-wife Lilith Sternin in the mix, none of them ever felt quite evenly matched for him in a way that would suggest longevity. Of course, nearing its looming series end, Frasier worked to rectify that fact in its final season. And boy, did the series succeed with the introduction of Laura Linney's Charlotte Connor.

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Charlotte and Frasier meet through his true last-ditch attempts at finding love, since Charlotte is a professional matchmaker. But it just goes to show you that you'll often find what you're looking for in the least expected places, as they soon fall head over heels for one another. Linney's pitch perfect line deliveries and innate warmth elevate Charlotte to a class of her own when it comes to Frasier's love interests, and the series finale's ending - with Frasier setting off to Chicago to reunite with her - is all the more optimistic because of her casting.

Patrick Stewart (Alistair Burke)

Patrick Stewart as Alistair Burke in Frasier

Niles and Frasier like to imagine that they belong to a truly upper-crust crowd throughout the series, but arguably one of the most influential connections they make is with renowned conductor Alistair Burke, played by the one and only Patrick Stewart. Burke is openly gay, and due to a comedy of errors, he winds up with the impression that Frasier is, too - which leads to him courting the otherwise unabashedly heterosexual Dr. Crane.

Desperate for attention and high society life, Frasier plays along with the charade until the episode's final moments. And all the while, Alistair Burke is made instantly lovable and iconic in the series' history thanks to the total commitment of the legendary Stewart, his dry and pitch perfect delivery of every biting quip and flirtation.

Michael Keaton (Blaine Sternin)

Michael Keaton as Blaine Sternin in Frasier

As if Frasier and his family didn't have enough to deal with in the form of Lilith, Frasier doubles down on the Sternin family tree with the introduction of Michael Keaton's Blaine Sternin. An unapologetic grifter and total con artist, Blaine is astoundingly charming and always industrious. He has a reputation for stealing money from just about anyone, including Frasier himself, and has lived under many assumed aliases, including Royce Thibeaudeaux, Santana de la Cruz, and even Dr. Frasier Crane himself.

When Blaine arrives in town in Frasier, he is determined to show that he has changed his ways - but as anyone with a keen awareness of comedy can tell you, this is not the case at all. What follows is a truly hilarious battle of wills between Blaine and Frasier, as they try to one-up each other, and all of it buoyed by Keaton's impeccable comedic performance and total commitment to the absurd role.

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