He may be pushing 40. But when Kevin Hart got into that recording booth for "Captain Underpants: The First Epic Movie," the years evaporated.

"Ultimately we all went back to being a kid again," says Hart, 37, who voices a fourth grader in the animated adaptation of the popular children's book series.

https://www.youtube.com/watch?v=whdrgATtyWM

Tapping into that 9-year-old mindset meant throwing all acting caution to the wind, Hart tells Made in Hollywood reporter Patrick Stinson.

"You have every right and opportunity to be as crazy and wild as you want to be," Hart says. "You can always be dialed back. You don't ever want to be told to do more. So start off big and then slowly get pulled back. We all started off big. The performances when we first went in, because we were so excited, were kid-like performances."

"Captain Underpants" follows two overly imaginative pranksters named George (Hart) and Harold (Thomas Middleditch) who hypnotize their principal (Ed Helms) into thinking he's a ridiculously enthusiastic, incredibly dimwitted superhero named Captain Underpants.

"The success that this book has had is unbelievable," says Hart. "The opportunity to work in this movie and have any type of input or impact on it was huge."