Comic book characters have long been used for motivation in schools and workplaces. The most common influences involve Snoopy (Peanuts) and Garfield. Others like Calvin and Hobbes come to mind as well. Here are a few by Peanuts, Garfield and Archie.
It goes to show that sometimes The Sunday funnies can be rather inspiring and motivational as well as amusing. I know there are several more quotes out there from other comics as well as the same ones. However I may look deeper into more later.