Everything is the same. And everything is different.

And then again, everything is the same.

Yes, “Dear Evan Hansen,” which officially introduced Taylor Trensch as its new Evan on Thursday, is still a gut-punching, breathtaking knockout of a musical. But it is differently gut-punching and breathtaking now than it was during the year that Ben Platt led the cast.

It would have to be. Even before Mr. Platt opened the show on Broadway, he had been living with Evan Hansen for years: He played the role from the very first reading of the musical in 2014. In some ways it seemed that the authors (songs by Benj Pasek and Justin Paul; book by Steven Levenson) had sewn the character directly onto his skin.

Certainly he yowled as if they had; it’s difficult to recall another Broadway musical performance so saturated with pain and confusion. The role could absorb it, though; when Evan tries to comfort the family of Connor, a schoolmate who has committed suicide, their need for information gets tangled with his need to be noticed and a moral nightmare ensues. Also a practical nightmare, as the lies he tells, amplified by social media, return to haunt him. These are big issues.

Playing the anxiety-riddled high school senior, Mr. Platt provoked in the audience a reverse suspension of disbelief: As he cried and belted, often at the same time, it was hard not to fear for the actor’s own well-being. On the two occasions I saw him in the role, I wanted to dose myself afterward with a cocktail of Zoloft and Mucinex.