The newest adaptation of Stephen King’s It hits theaters this week, and the horror film’s Pennywise is set to scare audiences worldwide.

The shape-shifting entity was brought to life in the film with both practical make-up effects and CG, and with that in mind, SYFY WIRE looks back at how some of the best horror movie effects in history have been made.

In part one, we revisit a few of the most memorable "old-school" creature effects from the 1970s and '80s, and talk to Chris Walas, a master of make-up effects and animatronics and the man behind Jeff Goldblum’s transformation in The Fly.

Bursting onto the scene

Hollywood has been cranking out scary monsters and make-up effects since the beginning, but a set of horror films starting in the 1970s captured moviegoers' imaginations so much that they wanted to know just how those effects -- all practical -- were created. The incredible chest-bursting creature in Ridley Scott’s 1979 sci-fi horror Alien is a classic example.

That scene, in a film that also features fantastic full-sized animatronic puppets, saw actor John Hurt convulse in pain mid-meal as a tiny alien bursts from his chest and then dashes away. It was made possible by having Hurt first lie in a custom-made chair. A false chest piece and table were then positioned to make it look as if the dramatic moment was happening directly to him.

Video of Alien (2/5) Movie CLIP - Chestburster (1979) HD

For the actual chest piercing, a prosthetic baby alien was fixed to the top of a hydraulic ram. The effects crew, hidden under the table, set up special blood tubes and pumps that squirted at just the right moments. Scott had also made a request to use real pieces of animal intestines, liver, and offal -- don’t worry, it was all cleaned and sanitized beforehand.

Perhaps the most convincing part of the effect, however, was that the other actors were kept in the dark about exactly what was about to happen -- when it did, their reactions were real and visceral, partly because they all become covered in fake blood. It’s a sequence that has been copied, and parodied, in many films since, but never matched in scariness.

A transforming era of horror effects

Video of An American Werewolf in Paris

Effects were easily the star of John Landis’ An American Werewolf in London (1981). The movie showcased elaborated make-up effects, a werewolf creature that convincingly walked and attacked on screen, and most notably, a horrifying man-to-wolf transformation.

The artist behind that work was the revered Rick Baker, who won a make-up effects Oscar for the film (in fact, he’d go on to win another six Academy Awards for films such as Men in Black and The Wolfman). Equal parts comedy and horror film, An American Werewolf in London is still terrifying to watch for its confronting and bloody creature scenes and close-up looks at gory make-up.

The transformation itself relied on several methods of effects artistry, from gradual layers of hair and make-up being applied, to animatronics behind prosthetics that would gradually push out sections to make it appear as if the actor’s face and body were painfully changing. The most amazing feat? None of this was CG, which is almost surely how it might be done these days.

Keeping it old-school

The Fly (1986)

David Cronenberg’s The Fly (1986) is another classic horror pic that made ample use of transformation effects, this time to turn Jeff Goldblum’s scientist character into a fly hybrid after one of his experiments goes awry.

Chris Walas and Stephan Dupuis shared an Oscar for the make-up effects work, where they not only allowed Goldblum’s eccentric acting to shine through but also created a terrifying and sometimes fragile character in fly form. Walas told SYFY WIRE that, once fully transformed, the final creature -- nicknamed "Spacebug" -- actually involved two separate puppets.

“One was a full-sized mechanical rig operated by 12 people which was used for wider shots,” says Walas. “The other was a waist-up puppet with rod arms that was more articulated in the head and face that was used for close-ups. The very last puppet, which we called the Brundlepod, was a separate rod puppet that was operated from beneath the floor and that used the same head as the close-up puppet.”

Again, that stunning work for The Fly was absent any digital visual effects, but developments in realistic digital creatures were not too far away. Walas, who had also crafted the Gremlins in Joe Dante’s 1984 comedy horror film of the same name, is uniquely placed to have been part of what he calls the "practical effects heyday" of the 1980s, and then see the march into CG.

“While it’s absolutely astonishing what can be done these days digitally,” says Walas, “it’s fascinating for me to see that the fans are screaming for more practical effects, even those raised in the digital age.”

The effects master is indeed adamant that practical solutions are far from dead, especially in horror films. “With the advances of both techniques and materials in practical effects, much more is possible. That, added to the explosion of incredible talent on the scene now, bodes well for the future of practical creature effects, I think.”