Don gives everyone a shake-hug (hugging someone while patting them on the back or shoulder with one hand) which he calls "sugar." At first, Rigby hates him, but at the end of the episode "Don", Rigby finally gives Don some "sugar" and is on better terms with him. He is at least a year younger than Rigby and, despite being the younger brother, Don is the opposite of Rigby; Don is nonviolent and mature. He is still easily-relaxed and very nice to others, always offering sugar to possibly anyone, which made him more popular than Rigby. Don later admits that he did not want to overshadow Rigby, since he tried to be like Rigby as much as possible.
Currently Rigby and Don are reconciled and love each other like brothers and get along well as in the episode "Bank Shot" "The Thanksgiving Special", "Just Friends", and "Gymblonski". He was metioned in "Rigby in the sky with a Burrito", and "The Lunch Club".