W. Watts Biggers, who helped create the 1960s cartoon show "Underdog" and composed its catchy theme song, has died at 85 after suffering a heart attack, reports The New York Times.

Biggers and his co-creator, Chet Stover, were working at the advertising firm Dancer Fitzgerald Sample when they started working on a cartoon show that would promote General Mills cereals, the story says.

As they knew they’d be competing for a time slot against Jay Ward and Bill Scott, the co-creators of "Rocky & Bullwinkle," Biggers had the thought that they were the "underdog." Their character was born: a mere shoe shiner who became a hero when reporter Sweet Polly Purebread was in danger.

They won the spot.

Underdog was voiced by character actor Wally Cox and spoke in rhyming couplets. The show, which debuted in 1964 on NBC, grew in popularity, allowing Biggers and Stover to depart advertising and start a production company, Total Television, the story notes.

An Underdog balloon has been featured in the Macy’s Thanksgiving Day Parade, and the show is syndicated worldwide.

Here’s a clip of the show’s opening and theme: