Harley is Harry's obnoxious cousin, but as for which cousin's parents is related to which one, it is never known.
Harley takes certain advantages of Harry in the following episodes, to name a few:
- In "Harry's Sweet Job," Harley talks Harry into hiring him for the job when his only co-worker, Margaret, calls in sick, but he only does it so he can have free samples (which is not allowed). While Harry is spending his lunch break doing trapeze practice with a partner, Harley inconveniences a customer who asks for a box of truffles, with 4/8 hazelnut (meaning four out of eight truffles being hazelnut), 3/8 mocha, and 1/8 caramel, by eating the latter two kinds, leaving only the hazelnut ones. When Harry returns from his lunch break, receives the man's complaint, apologizes to him, and replaces the missing ones, he asks Harley if he knew what happened. Harley, with chocolate on his face, lies that he has no idea. As punishment, Harry responds, in chocolate letters and an apostrophe, that Harley is fired.
- In "Harry's Big Date", Harry plans a date only for himself and Jenna, but Harley talks him into taking him because of a bad day he is having, ruining Harry's budget, causing Harry to simply order a grilled cheese sandwich. As a result, to stick to the budget, Harry keeps talking Harley into not ordering any dessert so he can impress Jenna and stay on budget.
Harley is not a very good counselor, as in the segment "Harry Restores Balance," he forces the children to play games only he can win. Then he cheats in the recycling game.