Andrew Rannells and Rory O’Malley know a thing or two about groundbreaking, hit Broadway musicals.

First, they originated the roles of Elder Price and Elder McKinley, respectively, in Broadway’s megahit The Book of Mormon. Then, when Jonathan Groff left Hamilton from October 27 through November 29 to film Looking, Rannells stepped in to play King George III. Now, as of April 11, O’Malley took over as the sassy monarch when Groff departed the show for good.

These two shows have the type of mainstream success that is rare for Broadway. “You can tell from the reaction outside in the world—that when people who I didn't even think knew what Broadway was are contacting me, asking me for tickets [to Hamilton], that this has crossed over into a part of the culture that I'm amazed by,” says O’Malley.

O’Malley and Rannells experienced that crossover appeal and frenzy for tickets before in The Book of Mormon. “The energy around Hamilton to me felt very similar to The Book of Mormon because people who were not interested in theatre were all of a sudden talking about our show,” says Rannells.

“I think that we all knew that Trey [Parker] and Matt [Stone] and Bobby [Lopez] [Mormon’s writers] have a very strong fan base and we knew that we would find an audience. I didn’t realize at the time how big the audience was going to be,” says Rannells. “I never could have imagined that it would be touring through Salt Lake City a few years later. I think we all thought [Mormon] was going to be a cool New York thing, but maybe wouldn’t live outside of Broadway, and instead it’s become this huge success that’s all over the world now.”

Still, the clues appeared early on that the reach extended far beyond theatre enthusiasts. “I remember after our first preview, a guy came up to me at the stage door and said, ‘This was the greatest thing I’ve ever seen. When does this air?’” says O’Malley. ”I said, ‘Oh no, you were out at a play tonight. This isn’t going to be on TV. We’re going to do it again tomorrow for a whole new audience. I realized then that there were going to be people coming to this show who had never been in a Broadway theatre and you certainly get the same sense from Hamilton.”

“All of a sudden we were in magazines that normally don’t cover Broadway things. All of a sudden we were in Entertainment Weekly and People Magazine,” Rannells says. Sound familiar?

But in terms of process, the Hamilton experience was inherently different for the two actors. Rannells and O’Malley worked on workshops and readings for years before it made it to Broadway, influencing the development of the musical.

Part of joining the show, rather than opening in it, means being a fan before being a cast member. “I watched that show at the Public and said, ‘This is the best thing I’ve ever seen,’“ says O’Malley. “It’s a crazy thing to be in this show within the first year.”

In fact, if things had gone differently, he would be playing Bill Gates in the musical Nerds on Broadway right now. He got the role in Hamilton 48-hours after Nerds was abruptly canceled, just weeks before the first preview. “I feel like I’m 13 years old and somebody has just asked me to join the cast of Les Mis, the show that I was obsessed with when I was 13.”

“It is something so big from the outside, so it’s scary in some ways. I certainly didn’t want to be the one that ruins this amazing piece of work,” O’Malley says, but he quickly learned that he couldn’t ruin it ”as long as I was honoring the writing.”

“You don’t have to go into it thinking, ‘How can I make this better? What do I need to do to make this work?’” says O’Malley. ”It already works.”

Rannells grounded himself by focusing on the work, always aware that the job is to “tell the story every night” eight times a week—a lesson that applied to Hamilton. “It’s actually comforting in a way because you always have that safety to go back to put on that costume and to tell that story,” Rannells says. “It felt like a very safe place to be in the theatre.”

As for stepping into the character of King George, “I‘m not above stealing from other actors,” says Rannells, who very closely observed Groff’s take on the role before stepping in, who in turn learned from his Public predecessor, Brian d’Aarcy James. “Brian laid beautiful groundwork for everybody who is going to play this part now.” Currently, that means O’Malley, but will certainly hold true for those next in the line of succession.

Linda Buchwald is a New York-based arts journalist focusing on theatre and television. Follow her on Twitter @PataphysicalSci.