Jerry Seinfeld at Andre Agassi Grand Slam for Children benefit at the MGM Grand, Las Vegas, Nevada - 06.10.07

The 53-year-old admits he's always been juvenile, and that this is the reason why he's had so much success.

He tells American magazine Parade, "I wouldn't even call myself a full-grown adult until probably my late 30s. What most people are at 25, I don't think I became until I was 38.

"I think there's a certain naivety that I have, a kind of juvenility that is really one of the keys to comedy."

Source: WENN