From Homestar Runner Wiki
Coach Zed is a name Strong Bad makes up for the Canadian pronunciation of Coach Z in the email "do over". Strong Bad then thinks that he would prefer calling Coach Z that name after saying it. He believes that after calling Coach Z Coach Zed, he wouldn't suck so bad. The "Z" emblem on Coach Z's body has been replaced with a "D". He is clearly drawn in the style of Charles Schulz, cartoonist of the famous "Peanuts" comic strip. He bears facial hair, a necklace and a rumpled fedora, just like Spike, one of Snoopy's brothers. He bears a slight resemblance to "Coach Backwards N" from the DVD Sketchbook.