Ventimiglia detailed to host Jimmy Fallon the experience of portraying a younger Jack during the show's recently concluded third season.
"To go backwards and do clean-shaven and war Jack, I had to make sure, and the writers make sure, that everything was still lining up toward that eventual Jack that we knew from the first season and the second season," the actor said.
"So it was challenging, but it was so rewarding," Ventimiglia continued before mentioning his "This is Us" co-star Mandy Moore who portrays Rebecca Pearson.
"What Mandy and I were able to discover in this newer, younger era of that love story was really wonderful," he said.
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