Harold's personality is similar to Johnny Test's father, Hugh Test from Johnny Test, although he doesn't possess the trait of being a top neat freak. In some ways, they are the exact opposite.
Harold's personality is also similar to Arwin from The Suite Life of Zack & Cody as both characters are played by Brian Stepanek.
Harold has an obsessive love for his car, which makes him go crazy from time to time. In fact, he keeps "Monique" a secret from his wife, which is similiar to the quirk shared by Timmy Turner's dad from The Fairly OddParents - who very much loves his car, the Striker Z (which, ironically, was a toy car he wanted as a kid), more than he loves his wife.
He is so cautious that he once earned a trophy for being cautious.
As shown in "Crumbs!" he loves his wife's home made cookies so much that he has developed a split personality that causes him to attack anyone who tries to keep them away from him.