Possible Clues:

• Holmes to Conan Doyle, e.g.
• Tony Clifton, to comic Andy Kaufman
• Change identity?
• Change, say, ring for very close friend
• Part of many a superhero's life
• Change nothing without, say, close friend
• Intimate pal to change and say nothing
• A second personality or intimate friend
• Singer embracing monarch, for example, as bosom pal
• Intimate nothing after change, say