By now, most fans know that the mask used in 1978's Halloween for killer Michael Myers was based upon William Shatner's face. The actor himself has never appeared in the franchise, and the use of the mask was inadvertent, according to Shatner in an interview with Comicbook. On top of that, Shatner doesn't earn a dime in royalties from the mask.
The mask was based upon a mold of the actor's face so that the Star Trek makeup team could use it to alter Captain Kirk's appearance if need be. This was a matter of convenience as the actor didn't have time to sit in a chair each time something on his face needed to be changed.
Shatner didn't know what happened to the mask after Star Trek was cancelled, but someone found it, and it ended up in a Halloween shop.
""That mask was made on my face to allow the makeup people at Star Trek to use it to apply appliances, beards, and mustaches and pieces of plastic that altered my appearance. They used that instead of using me, who didn't have the time to do that.- William Shatner
So at one point they didn't, the [Star Trek] series was canceled and I don't know what happened to the mask. Somebody found it and then it ended up in a Halloween thing [costume shop], and then my understanding of the story is the director of Halloween said, 'Go get a mask,' and somebody grabbed that mask. It's all inadvertent, as far as I know.""
As it turns out, Halloween’s production designer, Tommy Lee Wallace, purchased the mask from a Hallloween costume shop. He made the face and the eye holes wider and painted it white to make it appear essentially faceless. So to look at it straight on, the mask doesn't look anything like William Shatner. But the creation of the mask from Shatner's face is enough to give the actor a place in the Halloween franchise history...even if he doesn't get paid for that!