NEW YORK (AP) — Nickelodeon's "The Wonder Pets!" introduced preschoolers to classical music and opera during its first season. Now it's moving on to the Beatles.

It says something about the Beatles' continuing appeal that TV producers turned to a band that broke up nearly 40 years ago as the best way to introduce children under age five to rock 'n' roll.

"They were such brilliant songwriters that just cross over every age group," said series creator Josh Selig.

The "Save the Beetles!" episode premieres April 21 (7 p.m. EDT). The Wonder Pets travel to Liverpool to rescue four beetles whose yellow submarine is trapped in kelp. Following the rescue, the Beetles perform a concert.

The series features a guinea pig, duckling and turtle who travel the world to save baby animals in distress. Last year the music was recorded by a full orchestra with much of the dialogue sung in operetta style.

Lenie Colacino, a star of Broadway's late-'70s musical "Beatlemania," is the voice of Wingo, Jack and Pete (or Ringo, John and Paul) in the episode. He said he would have been happy to do George's "beetle," too, but producers wanted another voice.

He's continually impressed with how the Beatles' music moves on from generation to generation, and he likes how the story was told on "The Wonder Pets!"

"It wasn't smarmy," Colacino said. "It didn't talk down to children."