Halloween is a time for everyone to put on a mask and unleash their scary side. Though for some actors, that sounds like just another day at the office.

If you ran into one of them on the street you probably wouldn't recognize them, but after they disappear into their costumes and makeup, they become creatures you wouldn't want to meet in a dark alley. Click ahead to meet the men inside the monsters.

Photo by New Line Cinema/Courtesy Everett Collection, Eric Charbonneau/WireImage.comJASON VOORHEES
ACTOR: Derek Mears
MOVIE: Friday the 13th (2009)

The costume for Jason Voorhees might seem to be a relatively simple affair -- a machete, a hockey mask, and some fake blood should pretty much cover it. Yet Derek Mears, who plays the slasher in the most recent installment of the franchise, spent three and a half hours in the makeup chair to get himself into full Jason mode.

Photo by Warner Bros., Ron Galella/WireImage.comFREDDY KRUEGER
ACTOR: Robert Englund
MOVIE: Nightmare on Elm Street (1984)

Robert Englund has become a pop culture icon, thanks to his turn as everyone's favorite disfigured dream stalker. Yet even before he put on all that latex and that deadly glove, Englund impacted, if indirectly, another pop culture phenomenon. When he failed to land the role of Luke Skywalker in an audition, he told his friend to try out. His friend was Mark Hamill.

Photo by Dimension Films, Chris Polk/FilmMagic.comMICHAEL MYERS
ACTOR: Tyler Mane
MOVIE: Halloween (2007)

Mane plays a psycho-killer in both of Rob Zombie's "Halloween" movies, but his first line of work was only slightly less brutal: wrestling. Going under the name of "Nitro," the 6'8" Mane won the UWF MGM Grand Championship in 1994. When he learned that he landed the part of Myers, he reportedly watched every movie in the "Halloween" franchise consecutively.

Photo by Everett CollectionTHE PHANTOM
ACTOR: Lon Chaney Sr.
MOVIE: The Phantom of the Opera (1925)

Chaney was dubbed "The Man of a Thousand Faces" because of his ability to completely transform his visage for a role. For "Phantom," he jammed cotton into his cheeks, glued his ears to his head, and used rubber, spirit gum, and fish skin (yes, fish skin) to pull back his nose and flare his nostrils. The getup was extremely painful and his nose bled from the abuse, but the effort paid off in the end. Movie-goers reportedly fainted from shock at seeing the Phantom's ghoulish unmasked face.

Photo by Lions Gate Films/Courtesy Everett Collection, Tony Oudot/FilmMagic.comLEPRECHAUN
ACTOR: Warwick Davis
MOVIE: Leprechaun (1993)

Warwick Davis was a mere eleven years old when he was picked by George Lucas to play Wicket the Ewok in "Return of the Jedi." Since then, he's been in many sci-fi/fantasy movies from "Willow" to "Harry Potter and the Half-Blood Prince" to this movie where he plays a murderous imp with a pot of gold.

Photo by Picturehouse/Courtesy Everett Collection, Chris Polk/FilmMagic.comTHE FAUN
ACTOR: Doug Jones
MOVIE: Pan's Labyrinth (2006)

Doug Jones spent five hours in makeup for both his role as The Faun and the child-devouring Pale Man. Though his costumes left him mostly blind while standing on eight-inch lifts, his primary concern was one of language. Even though he spoke no Spanish, Jones insisted on delivering his lines, and he arduously memorized his parts while in makeup. In the end, though, director Guillermo del Toro had his lines dubbed by a Spanish actor.

Photo by Everett Collection, Everett CollectionFRANKENSTEIN'S MONSTER
ACTOR: Boris Karloff
MOVIE: Frankenstein (1931)

Karloff (born William Henry Pratt) became a star playing Frankenstein's monster and he went on to play the role again in two other movies. While shooting "Son of Frankenstein" (1939), his daughter was born, so he reportedly rushed to the hospital in full makeup.

Photo by New Line Cinema/Courtesy Everett Collection, Mark Sullivan/WireImage.comLEATHERFACE
ACTOR: Andrew Bryniarski
MOVIE: Texas Chainsaw Massacre (2003)

Bryniarski got his start in the movie biz when he was spotted by a talent scout while he was visiting a friend in L.A. A couple months later, he landed a part in "Hudson Hawk." Since then, his looming 6'5" presence has appeared in a string of flicks, most famously as a chainsaw-wielding lunatic with a penchant for strange headgear.

Photo by 20thCentFox/Courtesy Everett Collection, UnknownPREDATOR
ACTOR: Kevin Peter Hall
MOVIE: Predator (1987)

Jean-Claude Van Damme was originally slated to play the jungle-dwelling alien hunter, but the "Muscles from Brussels" stands at a mere 5'9" -- a less than intimidating height against the likes of Arnold Schwarzenegger and Jesse "The Body" Ventura. The filmmakers hired Hall instead, who stood 7' 4" -- a good fourteen inches above the Governator.

Photo by Everett Collection, Denise Truscello/WireImage.comGILL-MAN
ACTOR: Ben Chapman
MOVIE: Creature From the Black Lagoon (1954)

Chapman's latex and rubber suit was so constricting that he was unable to sit down during the daily fourteen hour production day. When he wasn't shooting, Chapman would stand in the lake in the studio's back lot to keep from overheating.

Photo by The Kobal Collection/WireImage.com, Michael Hickey/WireImage.comDARTH VADER
ACTOR: David Prowse
MOVIE: Star Wars (1977)

Most people associate Vader with James Earl Jones, who did his voice. But the guy in the suit was David Prowse, a British bodybuilder and competitive weightlifter. Though at his prime Prowse stood at about 6'6", he has had to endure multiple operations for arthritis, which cut four inches off his height.

Photo by Everett Collection, J. Vespa/WireImage.comKING KONG
ACTOR: Rick Baker
MOVIE: King Kong (1976)

Rick Baker is a legend in the field of special makeup effects. He turned Michael Jackson into a werewolf in "Thriller" and Eddie Murphy into a fat woman in "Norbit." But his one major role in front of the camera was under pounds of fake fur, latex, and animatronic muscle as Kong. You can actually see his face in Peter Jackson's "King Kong" as a biplane pilot shooting at the great ape.

Photo by TriStar Pictures/Courtesy Everett Collection, Derek Storm/FilmMagic.comGODZILLA
ACTOR: Kenpachiro Satsuma
MOVIE: Godzilla Vs. Destroyah (1995)

Satsuma got his start in world of rubber-suited monsters in "Godzilla vs. the Smog Monster" (1972), playing the Smog Monster. Eventually, he worked his way up to play the fire-breathing big guy in ten movies. Working in those suits was no easy business. They're heavy and poorly ventilated. Satsuma regularly passed out on set because of lack of oxygen.