Joe Harris, an advertising illustrator who drew two cartoon figures that would become icons of the Baby Boomer generation – Underdog and the Trix “silly rabbit” – died last month at his home in Stamford, Conn. He was 89.

“Silly rabbit!,” Harris’ 1950s ad copy went, quickly becoming a common playground taunt and a lasting advertising catchphrase. “Trix are for kids!” Harris drew the long-eared, sneaky bunny with a taste for the colorful General Mills breakfast cereal.

In an era with fewer regulations separating commercials from the cartoons they interrupted, illustrator Harris and his writing/producing partners in what would become Total TeleVision – Chet Stover, W. Watts Biggers and Treadwell Covington – churned out low-budget but silly, charming Saturday morning cartoons like Tennessee Tuxedo, King Leonardo, Biggie Rat, Tooter Turtle and Mr. Wizard.

Their most enduring success came in 1964 with The Underdog Show, an NBC series about a weakling mutt, the “humble and lovable” Shoeshine Boy (voiced by Wally Cox) who transformed into the still-skinny but powerful, flying Underdog, usually to assist his very own Lois Lane named Sweet Polly Purebred against such evil doers as mad scientist Simon Bar Sinister and George Raft-styled wiseguy Riff Raff.

Merrie Harris Instagram

Harris also was credited with cowriting the series familiar theme song.

The character was resurrected in 2007 for the big-screen Disney live-action Underdog, with Jason Lee voicing the title character and Amy Adams doing Polly.

Harris, who also wrote the 2008 children’s book The Belly Book, died on March 26. His death was announced by his daughter Merrie Harris, who survives him, along with her two sisters Joelle Malec and Sophie Harris.

“May heaven be a big studio,” wrote Merrie Harris on her Instagram page announcing her father’s death.