McDonnell created "Mutts" in 1994. The strip's stark, clean lines, along with its humorous and ometimes philosophical writing, already have made it something of a cult classic. Charles Schulz has called it "one
of the best (comic strips) of all time."

McDonnell received the Harvey Award for "Best Syndicated Strip" in 1998. The award, named after Harvey Kurtzman, creator of "Mad Magazine," is the comic book industry's highest award. In November 1997, McDonnell was honored with the prestigious Adamson Statuette from the Swedish Academy of Comic Art for "Best International Comic Strip Artist." In 1998 "Mutts" and McDonnell also received the National Cartoonists Society's "Best Comic Strip of the Year Award" and Germany's Max and Moritz "International Cartoonist of the Year" award. In addition, McDonnell has twice received the Ark Trust's Genesis Award for outstanding contribution for animal rights by a cartoonist, first in 1997 and again in 1999.

McDonnell was born March 17, 1956, and raised in New Jersey, along with two brothers and a sister. He graduated with a bachelor's degree from the School of Visual Arts in New York City in 1978. While still in school, he sold a few illustrations to The Village Voice. McDonnell lives in New Jersey with his wife, Karen, his dog, Earl, and their cat, Meemow.