As one of the most popular science fiction/horror shows of all time, The X-Files is marked by a unique conspiracy-based mythology, exciting paranormal adventures, and the stellar chemistry between Special Agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson). As these two FBI agents investigate alien abductions and unexplainable phenomena, they encounter quite a few different (and often terrifying) creatures, some of which defy any logical explanation. While the series is known best for its over-arching alien conspiracy plot, there's no denying that the show's standard monster-of-the-week (MOTW) episodes were just as engaging, and oftentimes more exciting. With over 200 episodes and 11 seasons to choose from, there's bound to be a monster in there for everybody, so if you're looking for some of the best Mulder/Scully creature features (meaning, "no aliens allowed"), then look no further than these episodes below...

Season 1 - "Squeeze" / "Tooms"

With a season almost completely full of MOTW episodes, we couldn't just pick one. This epic two-parter introduces one of the scariest villains on the show, the elongating mutant known as Eugene Tooms (Doug Hutchinson). "Squeeze" is actually the first MOTW episode of the series, while "Tooms" is the first non-mytharc sequel that the show ever produced. With a villain like Tooms, it's obvious why series creator Chris Carter and the gang decided to bring him back - a stretching serial killer who can weasel his way into anywhere? It's amazing they didn't keep him around any longer as the danger and suspense, especially when he goes after Mulder and Scully, push our favorite agents to their absolute limits.

Monster of the Week: The mutant Eugene Victor Tooms

Season 2 - "The Host"

Move over Creature from the Black Lagoon, this iconic X-Files monster is the best deep-sea dweller out there. Or, at least the most frightening. No MOTW list would be complete without "The Host," and by extension the mythic Flukeman (played by writer Darin Morgan before he landed his first writing credit on the show). In this classic X-File, Mulder and Scully investigate a series of bizarre murders that all relate to a mysterious sewer creature that haunts the waterways of New Jersey. As it turns out, this parasitic creature is actually the product of the Chernobyl disaster, half-man and half-flukeworm, and somehow made it over to the United States. There's no doubt that this Chris Carter-penned classic is among the best that The X-Files has to offer, and to this day no creature from the series is as recognizable as the Flukeman himself.

Monster of the Week: Flukeman aka "Flukie"

Season 3 - "Quagmire"

There are plenty of amazing MOTW episodes in the first few seasons of The X-Files, but out of all those in Season 3, none feel as personal as "Quagmire." The episode's Moby Dick-like hunt for "Big Blue" (Mulder's very own Loch Ness Monster), and Scully's astute observation that Mulder is basically Captain Ahab, makes this one stand out among the rest. If you weren't afraid of water before, you might be by the end of this episode. Even though the episode features a terrifying monster that goes for the jugular (poor Queequeg), the best scene by far is the one shared between Mulder and Scully as they're stranded in the middle of the lake. It's a beautiful moment that's stuck with fans for years.

Monster of the Week: We won't spoil it for you...

Season 4 - "Home"

Not all monsters are paranormal, even though we often wish they were. No X-Files monster scared viewers more than the Peacock family did in the infamous episode "Home." As Mulder and Scully travel to rural Home, Pennsylvania, they discover a murderous family of inbreds who has lived on their land since the American Civil War. This episode feels more like The Texas Chain Saw Massacre than it does X-Files at times, and for good reason. In fact, "Home" was the very first episode to receive a "viewer discretion" warning ahead of the episode, and was actually banned from rerunning on the Fox network. Although it's still regarded as a favorite, it has haunted many for years. While some episodes on this list lean more comedic in nature, "Home" is a straight-up horror movie made for television that opens with a nighttime baby burial. Yikes.

Monster of the Week: The Peacock family

Season 5 - "Bad Blood"

No episode of The X-Files has a better teaser than this episode, and it's not even close. While Stephen King's "Chinga" is a close second, "Bad Blood" is one of the best MOTW there is, and certainly the best of Season 5. This hilarious mystery, written by Vince Gilligan, is told a bit out of order as Mulder and Scully reflect on their most recent case in "trailer park Texas" where Mulder (in rare form here, at least from Scully's point of view) thought he finally found a vampire. Whether he's right or wrong, things get a bit out-of-hand and, well, you've just got to watch this one because it's a genuine classic. Between Luke Wilson's guest appearance and the exaggerated takes on both of our favorite FBI agents, we've only got bloody good things to say about "Bad Blood."

Monster of the Week: Vampires, just not the kind you're picturing...

Season 6 - "Arcadia"

While "Drive" and "Triangle" might be most X-Philes' Season 6 go-to (and for good reasons), "Arcadia" definitely has the best monster, so we're going with this one. As Mulder and Scully go undercover in a neighborhood with a no-nonsense HOA, they uncover a domestic conspiracy revolving around the local homeowners' association, which turns out to be deadlier than they'd hoped. As our favorite duo "play house" as they go undercover, a Tibetan thought-form (called a Tulpa) threatens anyone who opposes the rule of the association, with a punishment of death. From what we can see through the darkness, the monster is pretty scary, but in truth, it's the creature's relentlessness (and the other homeowner's intentional ignorance) that's especially terrifying. More reasons not to move to suburbia!

Monster of the Week: Tulpa (the Ubermenscher)

RELATED: The 25 Best Episodes of 'The X-Files,' Ranked

Season 7 - "X-Cops"

Some might feel that "X-Cops" is a bit tacky, but it's one of the most remarkable episodes of the show, if not just for its technical value. Beyond that though, this Cops crossover stands out for having a unique monster, one who we don't actually get to see and can only be beaten by facing your own fears. It's an excellent episode of The X-Files, and one that reminds us of just how much crap Mulder consistently puts Scully through (he originally dragged her to L.A. to find a werewolf). Of course, in the end, it's all worth it, and while there might be other more interesting MOTW episodes from Season 7 (such as "Millennium" or "Orison") there's no denying that fear is the most frightening monster of all. "X-Cops" is one of the best episodes of the show, and proved that even after seven years, The X-Files was going strong.

Monster of the Week: An unknown fear entity

Season 8 - "Roadrunners"

Sadly, not every episode on this list will feature the Mulder/Scully back-and-forth, but it's not our fault, you can blame David Duchovny! Thankfully, Scully, being the badass she is, survived without Mulder for quite some time. In "Roadrunners," she goes off to Utah on her own, still reeling from Mulder's abduction, to investigate a murder, but it turns out to be a bit more cultish than that. As Scully uncovers a group of religious extremists, she discovers that they believe a parasitic slug is the Second Coming of Christ. The cult aside, this episode marks the true beginnings of a functional partnership between Scully and John Doggett (Robert Patrick), who was often unfairly hated because he wasn't Mulder. If you're looking for a cult-fueled creature feature, then "Roadrunners" is the episode for you!

Monster of the Week: A spinal parasite and an eccentric "End Times" cult

Season 9 - "Lord of the Flies"

Similar to the previous season, Season 9 featured basically zero Mulder, and the one episode he returns in (the original two-part series finale "The Truth") is about concluding the mythology rather than tracking down a blurry creature with Scully. In the meantime, John Doggett and Monica Reyes (Annabeth Gish) keep the X-Files afloat long after Mulder's second disappearance. While there are a few stellar MOTW episodes of Season 9, the episode with the best monsters is hands-down "Lord of the Flies." A classic coming-of-age story, this one follows Doggett, Reyes, and Scully as they attempt to uncover the truth behind the bizarre insect-related deaths in New Jersey that all connect to a mutant human/bug hybrid. It's creepy, steamy, and will make your skin crawl if you don't get eaten first...

Monster of the Week: Mutant insect-human hybrids

Season 10 - "Mulder & Scully Meet The Were-Monster"

This episode became an immediate favorite with fans once the revival series aired on TV, and it's pretty obvious why. The X-Files was known to venture into some wacky, semi-comedic spaces, and "Mulder & Scully Meet The Were-Monster" is a perfect example of how to do it right. Written and directed by X-Files and Millennium alum Darin Morgan, this episode takes Mulder on a journey of self-discovery as he questions his own faith in the supernatural while he and Scully track down a reptilian were-creature. Along the way, they meet the Kolchak-looking Guy Mann (Rhys Darby), who just so happens to be the actual monster, but we'll let him tell you his strange story...

Monster of the Week: Guy Mann aka the Were-Monster, oh and some other serial killer...

Season 11 - "Familiar"

While the two revival seasons (which sadly didn't even equal a full season of the original series) might be pretty hit-or-miss for some, there's no denying that they knocked their MOTW episodes out of the park. Out of all that Season 11 had to offer, no episode was more chilling than "Familiar." Not only is the demonic Mr. Chuckleteeth probably one of the scariest looking monsters to ever haunt our TV screens (and that's not even to mention the evil Teletubbie), but in an episode full of hellhounds, witchcraft, and child killings, the real villain manages to be infidelity that very literally destroys two families.

Monster of the Week: The classic demon/witch combo that also includes hellhounds, Mr. Chuckleteeth, and more!