With Joker repeating its box office dominance for the second weekend in a row, more and more viewers have likely asked, “Where do I know that guy from?” after his character, Hoyt Vaughn, memorably warns and fires Arthur Fleck (Joaquin Phoenix) from his beloved clown gig.

Due to the intensity of Phoenix’s role and the movie as a whole, potential castmembers, including Pais, were subject to one particular rule from their lead actor in order to be hired in Todd Phillips' film.

“I had a meeting with Todd," Pais tells The Hollywood Reporter. “He said, ‘I loved your tape. I just want to make sure that you’re not an asshole because one person on set can really ruin the whole vibe of the thing.’ Joaquin told Todd, ‘I don’t care who you cast, just make sure everybody is a really good actor — and no assholes.’ So, I guess I passed the test.”

Joker is the beginning of a very busy stretch for Pais who reunites with Rounders co-star Edward Norton in Motherless Brooklyn on Nov. 1. He also returns to the small screen to reprise his role as Stu Feldman on Showtime’s Ray Donovan — as well as a role in Kathryn Hahn’s HBO series, Mrs. Fletcher, which was created by The Leftovers co-creator Tom Perrotta.

In a recent conversation with THR, Pais discusses the particulars of shooting Joker, the 30th anniversary of his feature film debut alongside Joker co-star Robert De Niro and what it’s like to be “that guy” in Hollywood.

Did you get a chance to celebrate the 30th anniversary of Jacknife with Robert De Niro on the Joker red carpet?

Wow, is it really that long? Wow. I saw him at the table read; I didn’t see him on the red carpet since he wasn’t at the New York Film Festival. He was at the table read, and our paths had crossed a couple times. He always gives me a “How you doin', kid?” and a smile. He’s a real sweetheart. That was the first movie I did, and I learned so much just from that. Prior to that, I was just doing theater, mostly in East Village basements. The director would always say, “You have to be louder than the boiler room. Make your voice reach the back wall.” So, I remember when we rehearsed the [Jacknife] scene before we started shooting it, there was maybe 40 to 50 people in the crew. It was just a scene between me and De Niro, and I was talking so the whole crew could hear just out of habit. He would just talk to me, and then I would talk to the whole crew. Slowly, it began to sink in that it was just me and him. It was a great moment; he just pulled me right into it.

Do these types of full-circle moments happen relatively often?

They do. I was in Rounders and worked with Edward Norton. And now, I’m doing Motherless Brooklyn with him, which opens Nov. 1. We also did a movie called Leaves of Grass in between. So, yeah, it does circle back, and it’s always really sweet when it does.

Was there anything unusual about the Joker casting process?

When I get jobs, it’s maybe 50-50 an offer or I audition for it. As soon as I heard about Joaquin Phoenix, the Joker and that it was going to be shot like an independent film, I was like, “I just have to be in this.” I auditioned once with casting directors, and they were enthusiastic. They gave it to Todd, and then I had a meeting with Todd. He said, “I loved your tape. I just want to make sure that you’re not an asshole because one person on set can really ruin the whole vibe of the thing.” Joaquin told Todd, “I don’t care who you cast, just make sure everybody is a really good actor — and no assholes.” So, I guess I passed the test. That makes it official, right?

You opted to play an asshole (Hoyt Vaughn) instead.

(Laughs.) I played an asshole! Exactly right!

Did you audition with the office scene, or were you given fake sides?

It was fake sides. A lot of the initial press that was going out about the movie had my name saying that I was a hotel manager. So, I did it once, and I could tell the casting people were lighting up. They were like, “I can’t really say what this is about, but it’s a little bit showbiz-y.” That was being very generous on their part, and I probably shouldn’t say that they gave out that much information. It was all so top secret. Then, there was a period of time where they were unsure if they even wanted to let the actors read the full script because they were so concerned about it being leaked. After I met with Todd a couple times, they finally did, as it was clear that I wasn’t going to leak the script. After reading the script, I said, “This is the best script I’ve ever read.” It’s such an amazing character study. It’s such an organic evolution of what happens in our society when we don’t take care of people.

What was the day or two of shooting like?

I worked three days. The level of concentration, the level that we all knew Joaquin was going to bring to this created such a focused set. I felt like I had to bring my A-game, and everybody on the crew felt the same. There was very little extraneous work going on. Very often between a take, the sandwiches come out, and everybody starts chitchatting. And then, X amount of time tends to happen before it’s like, “Oh wait, let’s get back to shooting.” That was not happening on this. It was extremely focused, and it was a high level of concentration on everybody’s part. Everybody was bringing it.

You were the more active performer in the office scene as Joaquin was more passive, but when you’re acting in a scene with a performer like him, do you ever catch yourself observing at times?

I’m sure that happens. I teach a class called Committed Impulse, and one thing that we do in that class is that as soon as you’re aware that you’ve drifted — meaning you’ve gone into your head and left what’s visually in front of you — we just go, “I’m back,” as part of the training, and return to what’s in front of you. I’ve trained my whole career to bring myself back so that I’m in it. I felt like we were just connecting as those characters. It was more in between takes when he was just sitting there and somewhat holding on to the character, or just however he chose to be when we were not filming, then I was more of an observer. It’s like, “Wow, this is Joaquin Phoenix, one of my favorite actors.” It was more in between takes that I would go there, but when we were filming, we were both in it. I think you can feel that in the scene.

Since the movie evolved quite a bit during production, did your office scene change at all?

We did some improvisation, and some of that improvisation is in there. There were a couple takes where Todd just said, “Do whatever you want.” He could tell we were in the zone. So, I played around with being a little harsher with Arthur, and out of the improvisation, the scene evolved. The essence of the scene on the page was there, but there were definitely some pieces in the scene that were improvised.

Todd Phillips and Brett Cullen have both talked about how Joaquin would sometimes walk off set to “reset himself.” Did you experience that at all?

He wouldn’t walk off in the middle of a scene or anything. Sometimes, he would hang out in the room while they were resetting. Other times, he would go off to a chair in a very secluded area, and he would just hang out. But, I didn’t witness anything that was particularly unusual.

Why do you think Hoyt was so skeptical over the fact that Arthur would be picked on for as little as a sign? Even his fellow clownsmen ganged up on him. Did Hoyt simply not care either way as he was just trying to keep his client happy?

Yeah, I think he was trying to keep his client happy. There were some other lines in there that were basically saying, “I like you Arthur, but you keep screwing up.” So, it was not just this incident, but it was other things. And then, when the gun drops, that was the final straw that leads to Hoyt firing Arthur on the phone.

How did you shoot the phone call? Were you on set with Joaquin, out of frame, or did you ADR your side later?

We actually shot that scene on set, and Todd was on the phone with me. Todd was doing Joaquin’s lines. So, we shot that while in the office.

Was there anything that you shot that didn’t make it into the final cut?

I don’t think this piece was at the very beginning of the movie; I could be wrong about this as it was originally scripted. But, the opening scene as Arthur is putting on his makeup and he pulls his lips to make that smile, I’m in the reflection of the mirror, and me and the other guys were improvising while that was going on. You can see some of that if you focus on the mirror. We were just improvising so much stuff, and that stuff did not make it in other than you can hear us chattering in the background.

There are many different interpretations of this film. What’s the one that you’re leaning toward the most?

I’ve heard people say that they thought it was all happening from the insane asylum. When I read the script, I did not take it to mean that. I took it as a very linear story — not a flashback or fantasy. I could see how somebody could interpret it that way; I don’t interpret it that way.

Your bio refers to you as “That Guy,” which is a badge of honor in Hollywood because it means you’ve worked consistently to the point where you’re recognizable. Do you have to audition all that much for New York roles since every New York casting director likely knows what you can do by now?

All the casting directors know what I can do, but it’s more if the director does. And I would say that the majority of directors know what I can do, but I’ve done so many different things and so many different kinds of characters. Just in the four projects that I have coming out in the next few weeks, well, Joker is already out, but Motherless Brooklyn, Ray Donovan and Mrs. Fletcher, those are four very different characters.... So, I’m not really pegged as, “Oh, that’s what that guy does,” which can be a plus, but then there are times where I do have to audition because somebody knows me as something and they can’t imagine me as something else. It’s interesting — the bigger projects I tend to get offers for and some of the smaller roles I have to audition for.

Do you get a ton of strange looks from people on the street who can’t quite place you?

I get that, but it’s more like people feel like they know me. There’s a percentage of people who feel like they know me from summer camp, and then there’s people who know my work and give me this: “Oh, I know who you are” — almost like they’ve cracked the code. Just about every day, I’ll get, “Did I meet you at blah blah blah?” and I’m like, “No.” Then, if the conversation goes on, I’ll go, “I’m an actor,” and they’ll say, “No, it’s not that.” So, the same conversation happens every day, but I just let it roll. It’s interesting because there are other actors who’ve had this kind of career, but it’s still kind of unusual.