Screenwriting : Character Reveal in Script by Imo Wimana Chadband

There are two issues regarding this. One is, you're trying to keep someone's identity a mystery until a certain point, when that character's identity is revealed in the "A-ha!" moment. If that's the case, then you'd write a line of description like the following:

For clarity, The Man in Black is now known as HAND GRENADE HENRY.

If prior to that, we SEE or HEAR The Man in Black, refer to him appropriately in your action lines and character name headings.

The other reason is that you're not trying to keep their identity a secret, but because they just haven't spoken until the "reveal". If that's the case, I'd still identify them in the action line prior to the reveal with a name, and describe who they are in that first time I state their name in the action line. Even if they don't speak until later, or if the character's identity/purpose isn't revealed in the story/to the audience until later, It makes things easier for production and continuity reasons, and for the person reading your script.

If you're doing it for some other reason, please state that reason.

Best fortunes to you in your creative endeavors, Imo!

Bill Costantini Interesting points. The second reason is more what it is, but, the thing is, they pop up in earlier parts of the script right, and the way they enter the script leads the reader to formulate that they serve a certain role, but when more of his actions start becoming clearer later on, then it comes to light that who they think he was, isn't actually who he was. So I can give the name when first introduced, but if I give the description, then the twist waiting to spring later on will be no more.

So given that instance, is it okay, to simply give him a name in his first appearance, and then when the twist happens to describe who he really is?

Are you saying that the character just changes - like, instead of being an "ally" , is really an "enemy", or that their real motives were hidden in earlier actions, or something like that?

I personally like to make it clear to my reader what WE SEE and what WE HEAR at whatever moment it is in the story. If we don't see or hear "the twist" - or, in your case, a character's true purpose - until a certain later point, then I don't write that until later on, when it actually happens, or foreshadow it/drop hints/show other scenes where things might be changing at the appropriate times. Like, I'm not gonna write:

IMO, righteous surfboard shop owner who is really going to try and assassinate BILL later, honorably sells him a surfboard.

When characters' roles change/true intents change throughout a story. I'd write that as it happens. In the script for Angel Heart, we don't know Louis' real role and intent until later. We don't know Harry's, either. Same thing with John Milton in The Devil's Advocate. In Point Break, we know Bodhi and Johnny's role/intent in the beginning, but they don't, and they learn them at the appropriate times, too. It's up to you as the writer to reveal things in the way you want to reveal them, in instances like these.

I hope I'm answering your question properly

Best fortunes in your creative endeavors, Imo!

You're definitely giving insight to what I'm asking. Thank you Bill Costantini

Using that scenario you just used. In my instance it would be like:

"IMO, righteous surfboard shop owner, honorably sells BILL a surfboard, assuring him it's the best on the market.

EXT. BEACH - DAY

We see BILL, surfboard in hand as he begins paddling into the roaring waves. He jumps up, catches his flow, and dances with the ocean, following the wave's toes as it guides him inward.

THEN-

TRAGEDY!

BILL disappears beneath the surface. The surfboard SNAPS!

INT. SURFBOARD SHOP - SAME

IMO stares through the open window. A smirk delights his face. He reaches for his phone-dials. A voice answers, we make out the haunting tone...IT'S JIGSAW-BILL'S ENEMY"

Sort of like that. where we thought IMO was only simply a man with best intentions for BILL by the way he operated with BILL at his store, but turned out to be in cahoots with his enemy scheming to end his life. So in that scene I just wrote, was the reveal correct? When we first saw IMO we went along with the description as if he was no threat, but then later revealed his true nature.

Yes, exactly. That's like, one fell swoop, and not in steps. You set it up to look like one thing, and then it becomes another. Good job, Imo.

Best fortunes in your creative endeavors, Imo!

Thank you so much for your input Bill Costantini I appreciate it. I have a better understanding of how to bring it across now in my script.

Best fortunes to you on your creative journey as well my friend!