I Have A Feeling
Dan's character in I Have A Feeling runs a business with his best friend. His life seems to get more confusing over the days, while his company is about to go under. His name has never been mentioned. He is also in The Life of a Big Boy as Aaron's best friend - he is the first to remember Aaron's birthday and reminds him that he is now an adult. His unnamed character is basically to blame for the entire series.
Dan's character first appears in I Have A Feeling #1, where he starts his day like any other, working for his business. He also appears in The Life of a Big Boy #1 as Aaron's friend that gives him coffee on his 18th birthday.