Chris Carter's sci-fi hit The X-Files is one of the biggest shows of the 1990s, a pop culture touchstone, and one of the classics that should be mandatory viewing for anyone. The show's original run lasted for nine seasons, ending in 2002. A sequel film was released in 2008, the show was revived with a short six-episode season 10 in 2016, and the eleventh (and presumably final) season was released in 2018.

Over the course of the show's eleven-season run, a lot of outstanding episodes were made that featured the talents of some of the best writers and actors on television. A myriad of actors made guest appearances portraying all kinds of characters. Choosing the best ones was certainly no easy task, but we've narrowed it down to these twelve.

ED ASNER AND LILY TOMLIN

Ed Asner Lily Tomlin The X-Files

In the season six holiday episode titled “How the Ghosts Stole Christmas”, Mulder and Scully end up spending Christmas Eve trapped in a haunted house with two ghosts who are inclined to give insight into the personalities of the two agents and their relationship.

The two apparitions are portrayed by Ed Asner and Lily Tomlin, whose pitch-perfect comedic timing and dry wit combined with Mulder and Scully's panicked strictly platonic partners makes for forty-four minutes of brilliant comedy. As the ghosts do their best to get inside Mulder and Scully's heads, scare the living hell out of them, and then turn them against each other, we can't help but laugh at their silly antics.

BRIAN HUSKEY

Brian Huskey in X-Files

Hands down, the best episode of season eleven is Darin Morgan’s “The Lost Art of Forehead Sweat”. Hilarious and smart, it’s a true Darin Morgan classic and will be remembered for years to come. The episode revolves around the so-called Mandela Effect, lampooning the series itself in a witty and hilarious manner and commenting on current socio-political issues.

The episode guest-stars Brian Huskey as Reggie – a mentally unstable man (or is he?) who claimed to have created the X-Files but that Mulder and Scully forgot all about him because of the Mandela Effect (or was it the Mengele Effect?) and the mysterious Dr. They. He tells a number of bizarre stories that take us back to classic X-Files episodes with some significant differences. But was Reggie really crazy, or has everyone else simply been whammied? Well, there's no clear answer, so it’s up to you to decide.

RHYS DARBY

The X-Files Rhys Darby

The Easter-egg-packed “Mulder and Scully Meet the Were-Monster” is, by and large, the best season 10 episode that restored the beloved sci-fi show to its glory days. Written and directed by the brilliant Darin Morgan, the Were-Monster episode tells the story of the scariest monster of them all – us. Portrayed by Rhys Darby, Guy Mann is a lizard creature who gets bitten by a human and is thus cursed to transform into a human during the day.

It’s an episode that’s as funny as it is clever. Guy's breakdown brought on by the pitfalls of everyday life offers some profound insights into what it means to be human. His nihilistic perception of what human life, which he summarized as craving a job you don't enjoy, worrying about mortgage and saving money, and lying about your sex life, is both tragic and comedic. One of the reasons this episode was as great as it was, is definitely Rhys Darby's outstanding performance.

MICHAEL MCKEAN

The X-Files Michael McKean

Michael McKean made his first guest star appearance on The X-Files in the season six two-parter “Dreamland”. McKean portrayed Morris Fletcher, a Man in Black working at Area 51, who after a freaky incident, swaps bodies with Mulder. Seeing this as an opportunity to escape a life he hates, Fletcher decides to live as Mulder, while Mulder takes this opportunity to snoop around Area 51.

However, when he starts slapping Scully’s posterior and sucking up to the top brass, it doesn’t take long for Scully to figure him out. In the end, everything is set back to normal and everyone involved forgets everything that happened during the switch. McKean, who has a knack for portraying slimy jerks, brings his A-game and delivers a hilarious performance in one of the finest X-Files episodes. Carter must have liked him too, since McKean was brought on for two more X-Files episodes.

BRYAN CRANSTON

Bryan Cranston in the X-Files

Before he was Walter White on the hit series Breaking Bad, Bryan Cranston made a guest appearance on an episode of The X-Files, which would go on to serve as inspiration for the character of Walter White. Written by Vince Gilligan, the creator of Breaking Bad, season six episode “Drive” is about an unlikeable racist, played by Cranston, whom Mulder must drive west to prevent from dying.

Thanks to Gilligan's topnotch writing, by the end of the episode you start feeling sorry for this awful piece of work, which is exactly what Gilligan set out to achieve when he created Walter White. Cranston’s performance in “Drive” was nothing short of brilliant and impressed Gilligan enough to pitch Breaking Bad to AMC with Cranston as the star of the show.

BRAD DOURIF

Brad Dourif The X-Files

Season one of The X-Files was a bit hit or miss. Episode thirteen, “Beyond the Sea” is one of the best the season has to offer and a lot of its success is owed to Brad Dourif, who guest-starred as Luther Lee Boggs. Boggs was a criminal on death row who claimed to be a psychic, offering Mulder and Scully clues about their on-going case.

Dourif’s performance is disturbing in all the right ways, as he portrays a myriad of characters in a single episode. From a man possessed by evil spirits to a weak man too afraid to meet the inevitable judgment that awaits him... and even a glimpse of a rebellious teenaged Scully. Dourif’s over-the-top mannerisms, his facial expressions, and especially his eyes, that appear to stare into his own personal abyss, made Boggs an unforgettable character.

ROBERT WISDEN

The X-Files Robert Wisden

Described by Scully as “a little man who wishes he were someone big”, Robert Patrick Modell is one of the creepiest villains ever to appear on The X-Files. Due to an accident, Modell gained the ability to control people’s minds with just his voice. For example, he managed to convince a man he was having a fatal heart attack over a phone. With his talent, Modell became a contract killer known as “Pusher”, due to his ability to push his will onto other people.

Portrayed by Robert Wisden, whose hypnotically smooth voice was the perfect fit for the part, Modell appeared in two episodes and thoroughly traumatized Mulder and Scully, as well as us watching the show. Suffice it to say, that the words “cerulean blue” will always give us the chills.

STEVE RAILSBACK

The X-Files Steve Railsback

Appearing in the season two two-parter, "Duane Barry" and "Ascension", Duane Barry is one of the most significant characters when it comes to the X-Files mythology. After all, his actions directly set the course Mulder and Scully’s lives would take. Despite only appearing in two episodes, Duane Barry was a complex character. From the very first scene, it was a toss-up as to whether he was actually an alien abductee or just a disturbed, delusional man.

To portray such a character convincingly one must possess the necessary acting chops, which Steve Railsback certainly does. Railsback portrayed Duane with such nuance and feeling that, even though he’s done some pretty horrible things, we can still feel pity for this broken man. His compelling performance will forever remain etched in our memory.

CARRIE HAMILTON

Carrie Hamilton The X-Files

Time loop episodes are a dime a dozen, and they almost always involve the main character trying to break the loop. What makes the X-Files’ time loop episode “Monday” stand out from the rest is that the character who’s aware of the time loop is a guest character we see for the first time and will never see again. This is quite the gamble as the writers need to actually make us care about this new character in very little time.

Luckily, Vince Gilligan and John Shiban created a character with a compelling background story and cast Carrie Hamilton who carried the episode from start to finish. The story of Hamilton’s character, Pam, spells out tragedy from the very beginning. Her life is obviously been one of constant struggle and she’s been trapped in this time loop for who knows how long. In the end, she pays the ultimate price to break it.

DOUG HUTCHISON

The X-Files Doug Hutchison

The X-Files had a fair share of both hilarious and scary “monster of the week” episodes. Season one episodes “Squeeze” and “Tooms” definitely fall in the latter category. Eugene Victor Tooms, portrayed by Doug Hutchison, is one of the first and best X-Files monsters of the week. He had the ability to squeeze through any opening no matter how small, and lived to be 121 years old by slipping into 30-year-long hibernation periods and feeding on human livers in between.

Hutchison’s portrayal of Tooms is one of the most iconic performances the show has to offer. Shark-eyed and disturbingly inhuman in every scene, Tooms made our skin crawl whenever he appeared on the screen. There’s something so brilliantly perverse and foreboding about him that to this day ventilation shafts make us a bit uneasy.

LUKE WILSON

Luke Wilson wearing a cowboy hat on X-Files

The fan-favorite season five episode “Bad Blood”, written by Vince Gilligan, offers the same story from two points of view: Scully’s and Mulder’s. It’s one of the most hilarious and brilliant episodes, and one of Gillian Anderson’s favorites.

As Scully and Mulder recount their very different version of the events that led to Mulder driving a stake through the heart of a suspected teenage vampire, we get to meet two equally different versions of the local Sheriff Lucius Hartwell. Portrayed by the perfectly cast Luke Wilson, the Sheriff is handsome, charming, and good at his job in Scully's story. While in Mulder’s version, he’s incompetent, unattractive with buckteeth and a rather awkward demeanor. Wilson was superb at portraying both the charismatic and the cartoonishly silly version of the character.

PETER BOYLE

The X-Files Peter Boyle

In yet another fan-favorite, critically acclaimed masterpiece penned by Darin Morgan “Clyde Bruckman’s Final Repose”, Mulder and Scully are on the hunt for a killer who targets psychics. They get involved with an old insurance salesman who has the ability to tell when someone will die. Portrayed with such sensitivity by the late Peter Boyle, Clyde Bruckman is both heartbreaking and hilarious.

He offers crude remarks about the crimes, playfully implies that Mulder will die of autoerotic asphyxiation and that Scully won’t die at all, audaciously flirts with Scully, and yet thanks to Boyle's outstanding acting skills at no point does the character lose our sympathies. For his wonderful portrayal of the cynical psychic Peter Boyle won an Emmy for Outstanding Guest Star Actor in a Drama Series, while Darin Morgan was awarded one for Outstanding Writing for a Drama Series. “Clyde Bruckman’s Final Repose” explores our relationship with life and death within a beautifully written narrative that Boyle was able to take to new heights.

NEXT: 5 Best Monsters On The X-Files (And The 5 Worst)