User blog comment:Mnenyver/Zeetha and Krosp/@comment-216.134.192.36-20100111144730

Nah. Any sidekick character primarily exists for the protagonist to explain things to. (Holmas and Watson, Dr. Who and Sarah Jane, etc.) Otherwise the writer has to resort to exposition or inner dialog -- and it's difficult to use the latter when you rely on withholding information from the reader to maintain suspense. So yeah, you COULD interpret them as imaginary, since they're there as a replacement for inner dialog, but you're just adding an undeeded layer of complexity.