Zaphod is hedonistic and irresponsible, narcissistic almost to the point of solipsism, and often extremely insensitive to the feelings of those around him. In the books and radio series, he is nevertheless quite charismatic which causes many characters to ignore his other flaws. Douglas Adams claimed that he based Zaphod on an old friend of his from Cambridge called Johnny Simpson, who "had that nervous sort of hyperenergetic way of trying to appear relaxed.