Talk:Imaginary Friend
What I find quite interesting with this page and concept is how there's so much variation within it. Some of the 'imaginary friends' are more like split personalities, while others seem like 'spirit guides' - I would certainly put Vimes' inner watchman and Rincewind's conscience in the latter category as, while they take on a life of their own, they influence, guide and generally aid the person they're associated with, rather than actually taking charge of the person and leading a life that's known of/noticeably different to other people.
In other cultures spirit guides (that to most westerners apart from some new-age-y types would seem little more than imaginary friends and something people "should" grow out of) are often quite accepted and can fulfill roles similar to the inner watchman/conscience.
Altogether Andrews may be another example of the more 'split personality' type.