One of Chavis' standout moments in the series occurred in the ninth episode of the first season. During young Randall's karate initiation, his father, Jack Pearson (Milo Ventimiglia), metaphorically proved to his 9-year-old son that he was his foundation, and would carry him through all of life's obstacles, no matter how big or small. For the scene, Ventimiglia had to do push-ups with Chavis on his back.
"As I was shooting it, I was actually about to cry," Chavis told ET's Denny Directo. "Because it was such a good moment that -- it just makes you feel all tingly inside. You just wonder, like, 'Why am I here?'"
The night before, Ventimiglia stopped by The Late Late Show and told Stephen Colbert that editors told him he did 223 total push-ups with Chavis on his back.
"Oh, yeah. Because there were a lot of rehearsals, and… yeah, " Chavis confirmed. "We worked for, like, five hours. Probably more than five hours, actually. We worked for like half of a whole day."
"I kind of felt bad, a little bit," he joked, when asked how tough that must have been for Ventimiglia. "At the half when we were almost about to be over, I kind of felt bad a little bit. He was actually keeping it really up, I was like, 'Wow.' But then I started to get tired."
Chavis also told ET that his TV parents, Ventimiglia and Mandy Moore, have met his real-life parents plenty of times. They've become so close, in fact, that they all act like a real family.
"We've been working from last summer to this summer so it's almost been a year, pretty much. We've really bonded," Chavis shared. "They always get a chance [to hang out together]. Like, one time when my dad took me [to set], Milo and my dad were talking a lot … they were laughing a lot."
Despite his close connection with his onscreen parents, Chavis admitted he's closest with Parker Bates, who portrays young Kevin.
"I have a lot of scenes with him," he explained. "In between takes, we make funny jokes, like, when we're sitting in our cast chairs … and Miss Marie, our set teacher, she used to play math games with us, which was really fun. What's weird is, they're actually fun. It's funny because when we're on a break, we're all like, 'Let's do math games!'"
Before the interview wrapped, we had to ask Chavis to spill some season two secrets. While he couldn't tell us much, he did give us a warning: "Get your tissues ready!"
Oh, they're ready, alright!
For more highlights on Ventimiglia's standout performance in This Is Us, watch the video below.