He is actually Rigby's younger brother (despite him being of larger size and having a deeper voice than Rigby). Don admires Rigby and attempts to be like him; for example, Don claims that he stopped wearing clothes because Rigby started walking around naked. Despite this, Rigby resents Don because everyone seems to prefer Don's company over his own. While Rigby is poorly educated, usually penniless and hardly gets things done, Don is an accomplished accountant, drives a Corvette and has his own house.