Movie monsters have proved to be fertile material for actors. Boris Karloff became one of the most popular film stars of the 1930s after his turn as Frankenstein’s monster elicited both sympathy and horror. Robert Englund’s comic timing as Freddy Krueger carried the “Nightmare on Elm Street” series through eight films. Bill Skarsgard even generated Oscar chatter for his unpredictable take on Pennywise in last year’s “It.”

Compared with them, Michael Myers, the masked killer in the “Halloween” movies, is not exactly a juicy role. He is silent and does not emote. He just stalks and kills, like a land shark in coveralls. In the original 1978 film, the character was billed as the Shape. How do you portray something called the Shape?

The answer is unexpectedly complicated.

Eight actors have tried to play him over 10 films, not counting “Halloween III: Season of the Witch” — which didn’t feature Michael — but including the many sequels, remakes, re-imaginings and reboots, the latest of which, simply titled “Halloween,” opened Friday.

John Carpenter, who directed and wrote, with Debra Hill, the original, described the character during a recent phone interview: “He wasn’t human and he wasn’t supernatural. He was somewhere in between. He was the Shape. He could be anywhere at night. He could be in the shadows. He’d watch you. And even though he moved like a human being, there was something about him ... different.”