My friend just met Nick, literally 2 hours ago. This is what he said:
I saw and spoke to Nick Castle today at Comic Con and he confirmed that he definitely is in only one scene as MM (Laurie shooting the window scene), but he is in another as somebody else in a "cameo.”
Interesting to know.
Horrible if true 
Sorry I don’t believe it!
Well he is 70, I don’t blame him. He probably gave Courtney some pointers so that’s better than nothing. Also really liked what I saw of Courtney so far so i am satisfied.
I personally think it’s the hush, hush game going on. I wish people would get through their thick heads that ‘‘He is not allowed too say anything’’ 
This is upsetting to hear, seeing as they made such an emphasis on his return. Wasn’t he on set in coveralls for several days?
He was. Many, many days. It sucks if this is true
I think he will be the mechanic that gives Michael his jump suit also.
Purely a guess though.
I’m with Knightblake…I don’t believe it:)
So they basically used him for publicity if true.
My friend met him recently and he said he’s in every scene that Michael is in.
If this is true it would correlate w/ what JJC had said previously - that Castle was in one scene as The Shape and doesn’t walk. I was hoping he was just referring to the trailer. I imagine they probably filmed him doing multiple scenes as The Shape along w/ JJC and just used what worked best for the film. It is odd though how the film is being marketed. Even the official website puts his name in the cast under the female leads w/ no mention of JJC https://www.halloweenmovie.com/synopsis/
Wt
That may be false he most likely is saying that to not spoil the movie but, if it is true you can’t really blame the guy he is getting up there in age.
This right here… great way to transition the “passing of the torch” as well haha.
He could be the mechanic he kills to get the coveralls back
That would be cool
Well how will we actually know it’s Nick or Courtney?? In all interviews they just say Nick. You would think they would mention the other guy, he’s getting outshined by Nicks possible one scene.
This would explain why Nick was on set for a few days wearing the coveralls. He really could be in just once scene as Myers, and the cameo scene as the mechanic.
Does anyone have a screenshot from the trailer of the mechanic laying on the floor? Maybe we could tell by the guys body type? I swear it seemed like the mechanic was a lot heavier than Castle.