Flukman Episode: 'Host' Season 2

When a tanker carrying nuclear waste from the Chernobyl disaster arrived on US soil it brought with it the series' most celebrated and terrifying monster, the horrendous sewer-lurking Flukman.

Eugene Victor Tooms  Episodes: 'Squeeze' and 'Tooms'

This mutant, liver-munching contortionist serial killer crossed paths with Mulder and Scully on more than one occasion.

Cancer-Man  Episodes: Various

While far less scary looking than some other entries in this collection, Cancer-Man was a monster on the inside, casting a long sinister shadow over many of Mulder and Scully's most important investigations.

Mrs Peacock Episode: 'Home' Season 4

While investigating a bizarre backwoods family, Mulder and Scully discovered their inbred, bed-bound mother in the family cellar.

Wolf Man  Episode: 'Shapes' Season 1

While investigating a series of killings in Montana, Mulder and Scully came face-to-face with the unforgettable Wolf Man.

'Greys'  Episodes: Various

Usually appearing on Dana Scully's operating table, these extra-terrestrial creatures and the government's attempts to cover up their existence form the basis of many of the show's most memorable story lines.

Rob Roberts  Episode: 'Hungry' Season 7

Having a silly name was the least of Rob Roberts worries – he was much more concerned with his unhealthy addiction to human brains...

The Great Mutato  Episode: 'Post-Modern Prometheus' Season 5

This Elephant Man-style urban Frankenstein was the product of a mad scientist conducting experiments on the inhabitants of a small rural town.

Eve  Episode: 'Eve' Season 1

Eve was one of a collection of spooky identical clones, apparently able to communicate telepathically...

Luther Lee Boggs Episode: 'Beyond the Sea' Season 1

This death row inmate was purported to have psychic powers which gave him a unique and unrivalled insight into the crimes of another serial killer still on the loose. But it was his unnerving ability to communicate with (and make himself appear as) Scully's recently deceased father that really got under everyone's skin...