One performance can often make or break a movie, but the collective talents of the right ensemble can transform what looks good on paper into something truly special on the big screen. The SAG Awards have been honoring acting ensembles for 25 years, first TV shows and then quickly broadening to include films. This year, there are a multitude of ensembles to choose from. Along with such Oscar frontrunners as “A Star Is Born,” “Vice” and “Roma,” there are some unique ensembles that could find themselves in the running.

When director Jon M. Chu landed “Crazy Rich Asians” he knew without a truly talented cast he might be wasting what sadly was a rare opportunity in Hollywood, a film with an all-Asian cast. This was one film in which the acting choices had to be pitch perfect.

Chu knew that casting directors often have very short lists when it comes to Asian actors. And the longtime studio helmer has always been skeptical that those lists are comprehensive, especially when he knew actors who were not on those lists.

“I needed to make sure that Warner Bros. knew that we needed to spend the extra money and the time, and that casting directors on all parts of the world [knew] … to include an open casting call, to make sure our net was wide and that we could find the best ones,” Chu says. The roles were very specific. “Some very comedic, some more dramatic, some villains, some heroes. We knew that was gonna be hard to find no matter what and understood the magnitude of the efforts that we would have to do to find the right people for these roles.”

The open casting call led to recommendations for Awkwafina and Gemma Chan, but one of the key roles came from an unexpected source. Chu had already cast Constance Wu as the lead, Rachel, but still hadn’t landed on who would play Nick, her romantic partner. It was two weeks before they were about to hold major chemistry reads with Wu when the production’s accountant in Malaysia told them to check out Henry Golding’s Instagram and YouTube travel videos.

“I was very intrigued because rather than acting cool or trying to be cool, he was already very interesting,” Chu recalls. “And he was already a people person. You could see just the way he talked to the restaurateurs or the people of the tribe, that he was interested in listening to them. And that, in a way, was the most important thing for Nick, to have that ease and easy charm to him, not trying hard at all. And he had the English accent, too.”

Another production that reached far and wide was Ryan Coogler’s “Black Panther.” Longtime Marvel Studios casting director Sara Finn knew from the beginning she had to truly understand the complexity of the “Fruitvale Station” filmmaker’s vision to truly bring it to life. Coogler already knew he wanted Michael B. Jordan and Lupita Nyong’o involved, but landing on the rest of the large ensemble was truly a process.

“We reached as far as Africa and did this worldwide search for [the character of] Shuri,” Finn says. “So down to the very smallest roles, even the tribal elders, there was a process and a search because he wanted Wakanda to be vivid, and rich, beautiful, and even though it’s a fictional land, it should feel authentic. It should feel African.”

Two of the film’s breakouts, Winston Duke, who plays M’Baku, and Letitia Wright, who portrays the aforementioned Shuri, were practically unknowns when Coogler cast them years earlier.

“Letitia, honestly, she hadn’t even booked ‘Black Mirror’ when we tabbed her,” Finn says. “We were just purely going off her talent, and her chemistry read. She won the part.”

She adds: “Literally, I love that you’re profiling the entire ensemble. There’s so much that goes into it to make a very diverse group of actors in our case from different parts of the world blend seamlessly together on screen in one cohesive ensemble.”

Finding that perfect onscreen “family” was a major concern of “Mary Poppins Returns” director Rob Marshall. The “Chicago” helmer knew Emily Blunt and Lin-Manuel Miranda would shine in the leads, but with a cast that went from 8 to 91 years old every piece had to be perfect. Especially as everyone involved had to understand they were “looking for the truth.” And the three young Banks children, Anabel, John and Georgie, portrayed by Pixie Davis, Nathanael Saleh and Joel Dawson, were key.

“These were the three, and there was no one else. They each claimed their roles,” Marshall says. “I was so impressed with how they work. To have them in rehearsals was key because it’s at that time you create a company. The fact that we had the entire cast for rehearsals, [that’s how] you create a company. Everybody’s on the same page.”

Marshall asked his “Into the Woods” star Meryl Streep to play Topsy in one musical number and it turned out she was keen on starring in the film because of its message of hope. “Meryl was very clear about that,” Marshall says. “She goes, ‘This is what I want to do. In this climate right now, I want to be part of this film sending this message of hope out into the world.’ And I thought that was so true of everybody from Colin Firth, Ben Whishaw, Emily Mortimer, Angela Lansbury. Everybody wanted to be part of this. It was our first choices across the board and I was impressed with that, very impressed with that.”

Francine Maisler is a casting director whose credits include legendary ensembles such as “The Usual Suspects,” “Milk” and “Birdman.” Reuniting with Steve McQueen for “Widows” reminded her of the “12 Years a Slave’s” director’s skill for making what some might see as a potentially problematic casting choice as truly inspirational.

“Elizabeth Debicki is probably 6-foot-3 and you wouldn’t normally think that a 6-foot-3 actress opposite Viola Davis, Michelle Rodriguez. Cynthia Erivo, who’s not tall, might be dismissed because of her height,” Maisler says. “And I know that in other casting, sometimes people have said that. But Steve was like, ‘This is the real world. People are all different shapes and sizes. And I don’t care, you know, that she’s that tall. She’s the most amazing actress, and I think this is the real world.’ And that’s what he tries to capture.”

Sometimes a filmmaker of McQueen’s stature is able to recruit incredible talent to take on even the smallest of parts. Maisler notes that Manuel Garcia-Rulfo, who plays Michelle Rodriguez’s husband, put his ego aside in terms of the size of the role, to work with him McQueen. “Jon Bernthal [was] the same; he jumped because he wanted to work with Steve McQueen.”

For casting director Dixie Chassay, the thrill of “The Favourite” was that director Yorgos Lanthimos is not a conventional thinker and doesn’t think in a linear way. For “The Favourite,” that meant he didn’t want to adhere to normal constraints of a period film set at the turn of the 18th century.

“He likes to kind of play all different types of acting alongside one another,” Chassay says. “So, he’s sort of interested in decoding conventions of acting, which is why there was the street casting alongside an international [ensemble]. He’s just fearless, I think.”

That led to expected choices as his “Lobster” collaborators Rachel Weisz and Olivia Colman, but also Emma Stone, in her first British period piece, the up-and-coming Joe Alwyn and Nicholas Hoult in a rare comedic turn.

“I think that it’s such an ensemble piece that the three women are helming it, so they are right in getting the attention, but I do think the two young men are real nuggets of delight,” Chassay says. “Part of that is the context within which they’re in [that] ensemble is helped by these three very powerful female roles, and that they fall into that and kind of participate in that in a very characterful way.”

Oscar winner Barry Jenkins recruited an extensive ensemble for “If Beale Street Could Talk,” but despite screen tests with his two leads, Stephan James and KiKi Layne, how did he know the entire group would land on the rhythm and authenticity he was striving for? The one table read didn’t give him any assurances. It was the terrifying filming of a scene that featured eight actors in one living room that proved they all were on the same wavelength.

“It was lovely to watch the actors become generous because even with two cameras, there were times where half the cast was not on screen,” Jenkins says. “Just not on screen and they know that they’re not on screen, and yet they still have to give so much because it’s such a lengthy scene that there’s all these peaks and valleys and you want to be there for everyone else’s peaks.”

The moment Jenkins knew they landed the scene, however, was when Frank (Michael Beach) storms out of the apartment. Regina King, portraying Sharon, then made an unexpected but powerful choice.

“Regina says ‘Go on Joe, we don’t need you here,’” Jenkins says. “She tells Colman Domingo [who plays Joe] to leave and when Colman leaves, Regina went right to the door and without me telling her, runs right to the door, closed it behind them and locked it from the inside and then turned back to the rest of the women in scene and it flowed perfectly with the camera angles, but it also seemed to solidify, OK, there were these waves throughout the scene, throughout the sequence and all the actors meld intimately, to ride those waves.”