A day after “Dear Evan Hansen’s” world premiere at the Toronto International Film Festival, Platt recalls where it all began and how he had no idea what he was getting into.

Platt first met Benj Pasek and Justin Paul, who wrote the music and lyrics, at an audition for another project. The pair then went to see him perform in “The Book of Mormon” on Broadway, where they invited him to the first cold reading for an untitled project they were working on.

“I was given no information about subject matter or the character,” Platt said at the Variety Studio at TIFF presented by Canada Goose, where he appeared with co-stars Amandla Stenberg, Nik Dodani and Colton Ryan. “I think they wanted to see what happened spontaneously, serendipitously.”

“I remember being in a tiny, little rehearsal room in New York, Pearl Studios or something, and walking in,” he continued. “It was Rachel Bay Jones, Michael Park, Jennifer Laura Thompson, myself and some other people opening it up and reading it for the first time. Obviously, it’s come a long way since then. It’s changed a lot. But the voice of Evan and the freneticism and the emotionality was there from the very first day. It’s really exciting that all of those gems and the essences of what made it special are still here all the way to the film.”

“Dear Evan Hansen” contains major discussions of mental health and suicide, topics that have become increasingly relevant in the age of social media. 

“It is so easy now to read into or judge people off of the concept of self that they present to the world on social media,” said Amandla Stenberg, who plays Alana Beck in the film. “It’s so easy to see only one facet or narrative of their lives and not know what’s happening beyond that. It’s easy for us to make really, really critical, tough judgements of each other on the internet, easy to swim and get lost in the mess of all that. Hopefully the movie is a reminder of our shared humanity.”

“I’ve spent a lot of time with Evan, and it’s a very blurred line in terms of him and I and my own anxieties. In terms of the hyper-connectivity and social media of it all, the piece has always taught me and continues to teach me, in a new way in the film, how important it is to differentiate things that are virtual or made up or crafted and the things that are real and human and the connections that really matter.”

When the trailer for the film was released in May, Platt drew criticism online for his age — the actor is 27, while his character is a high school student. “Has no one seen ‘Grease’?” Stenberg joked.

Platt kept it simple: “I’m excited for people to see the movie. I think it’ll speak for itself.”