How hush-hush is the story behind “Cloverfield,” whose super-secret ads ensured that all anyone really knows is that it’s a monster movie? For a long time even the film’s up-and-coming star Michael Stahl-David was in the dark.

“Getting [the part] felt good,” Stahl-David recalls,  “but I had no idea what it was. We didn’t see a script until the first day of rehearsal.”

Until last Saturday, the actor wasn’t even able to see the finished product (opening Jan. 18), which has been buzzed about ever since its title-free, flying-Statue-of-Liberty-head-featuring trailer debuted before “Transformers” in July. In a nutshell—don't read on if you don't want to know anything—the movie's about Rob (Stahl-David), his friends and other New Yorkers fleeing a huge, hideous monster, and the whole movie is presented as urgent, shaky handheld video camera footage captured by Rob's friend Hud (T.J. Miller).

The movie’s release will finally put an end to months of Internet speculation, with debates ranging from what the movie would be called (at one point it seemed the flick might just be “1-18-08”) to the appearance and history of its featured monster. Some even wondered if the film may have a tie-in to producer J.J. Abrams’ other highly mysterious blog staple, “Lost.”

The result is a blockbuster-level marketing frenzy rare for a film without any big stars. That certainly benefits Stahl-David, 25, who left his hometown of Chicago for New York in 2005. So far, his only other major credit is a starring role in the short-lived NBC series “The Black Donnellys.”

We caught up with Stahl-David by phone while he hung in Brooklyn. Since we knew that even a newcomer is too savvy to spill the beans on any “Cloverfield” details, we found out how he’d react to a real-life monster and why “You cannot spit game” in a Starbucks hat.

The movie was deliberately made with actors that the public isn’t likely to recognize. Is that because Brad Pitt is immune to monsters?
Dude, I just wouldn’t believe it if a monster stepped to Brad Pitt and he didn’t just take it down. I’d be like, “Dude, that monster couldn’t take care of Brad Pitt. I don’t care how big it is. Brad Pitt will flick a cigarette in that dude’s eye and just go have sex with some hot girl. I don’t believe it.”

How would you react if a monster really did attack your town?
I think I’d pee myself. I really tried to seriously think about that. It’s like, how could you process that? How could you possibly process that? Your entire conception of what reality is is shaken now. It would be like pinching yourself. It would be like, “Did I take acid and forget? What is going on? This is not the real world.”

How would you prove to yourself that it was real?
I think it would be the people around me. Seeing everybody else reacting. “Are you seeing this?” “Yes, I’m seeing this. Everyone’s seeing this. This is all happening. It’s on the news. It’s real.”

Well, what can people do to protect themselves from monsters?
I don’t know if there’s anything you can do. I would just say get a video camera. Don’t dress in high heels. And consider a bike. It’s good in traffic.

Were you scared of monsters when you were younger?
I didn’t see a lot of monster movies. I was terrified of spiders. Tarantulas and stuff. I had a friend who had a big plastic tarantula and he would just bring it down from the closet and I would be just like a screaming girl and underneath the covers. So I wasn’t a big horror movie guy.

The movie’s shot with a first-person, on-the-ground style. Are you easily nauseous in movies like that, like “The Blair Witch Project”?
I actually kinda am. When those [first-person] video games first came out, I had a hard time with those. And watching the movie when it first started, I was like, “Uh, oh.” And two minutes into it I was fine. I think most people will be all right. If you know that’s a problem for you, just take a Motrin. I mean, that’s what my mom is going to do.

“Cloverfield” is a big break for you. What was going through your head in 2005 when you first went to New York?
“I hope I can get a play within a year. If I can get a play within a year, I’ll be doing really good.” And it’s true; a lot of people come to New York and never get their feet off the ground. It’s hard. So that was my goal. And I wanted really badly not to work at Starbucks. At that one I failed. I did work at Starbucks.

How long did it take for you to go back on the “No Starbucks” policy?
[Laughs] I don’t know. Not long. Three weeks? I literally had no waiter experience. I tried faking that a couple times and that didn’t work. I had no money. I was just like, “OK. Damn it. Here I am with that terrible [Starbucks] hat.” You cannot spit game in that hat. You just can’t. You know what, I shouldn’t say that. There’s probably baristas out there who are doing really well. But for me, the hat killed it. I could not mack in that hat.