The singer and actor walked the red carpet at the premiere of his new animated family film, Trolls
-- in which he both starred and served as musical producer – on Sunday, and he stopped to talk with ET's Cameron Mathison about his son's reaction to the adorable movie.
"I got to screen it before anybody. I had to screen it before everybody because I had to make sure all the music was working out," Timberlake said, explaining how Silas, whom he shares with wife Jessica Biel
, was already able to fall in love with the film.
"He knows all the characters already!" Timberlake revealed, when asked if Silas recognized his dad's voice in the movie. "It's crazy!"
"Congratulations on your four years of marriage!" Leila said, beaming.
"Oh thank you!" Timberlake said, getting down on his knees to be eye-level with ET’s special correspondent. "Take your time. Don't get married too fast, alright?... I'm trying to look out for your dad! Boys are ick!"
Leila, who said she wants to be a singer when she grows up, also asked the nine-time GRAMMY winner for advice on starting a career as a vocalist.
"Don't do it!" Timberlake joked. "No, I'm kidding. Practice, practice, practice. That's my advice."
"This is officially the first interview I've ever done on my knees," Timberlake added, laughing. "I gotta say, I'm really enjoying it."
"We made a joke the other day that we feel like our only job now is just to promote this movie," Timberlake said, laughing. "[But] it's always nice to be a part of a movie that brings so much happiness to people."
Trolls hits theaters Nov. 4.