Nope, it's not self portrait week; yea though, every morning I do bear a strong resemblance to one of the most epic sidekicks -- Chewbacca. Go ahead, do the Chewy Roar. It's a Pavlovian response to his mention, I fully understand. We, mere earthlings, couldn't translate his words; however, we totally grocked the body language and the intonation. Above all else, we knew Chewy had Han's back.
Sidekick Rule #1: Loyalty
Writers can do many, many things to their characters, but the unbreakable tenet is Thy Sidekick Shall Always Be Loyal. Said sidekick may not agree with the hero's choices, but the sidekick tags along. When plot devices prevent the sidekick from attending, hero gets in a world of trouble. (Solo-cicle, anyone? Anyone?)
Sidekick Rule #2: Contrast
Readers/viewers may not be consciously aware of the writer's device of contrasting the sidekick against the hero, but they instinctively recognize it. For all that Sherlock Holmes was abrasive and manipulative, Watson contrasted him by being a ladies' man who soothed the ruffled feathers and managed the hoi-polloi. Had the reader been denied Watson's view of Holmes, the reader would only have seen a jackass of a genius. Had the audience been introduced to Moriarty via a sidekick, he might not have been such a villain. The same character device was used in a New Jersey Hospital when TV writers paired Dr. Wilson with Dr. I-Put-The-Ass-In-Acerbic House.
Yesterday, the debate over whether sex breaks the sidekick-hero dynamic came up in the comments section of Laura's post. Sex is not the intimacy to which I refer here; rather, the depth of knowledge about the hero to which no one else in the story is privy. They have unusual insight into the hero's character. Through the interaction of sidekick and hero, the audience is exposed to the motivations of the guy for whom we are supposed to root -- for better or worse. Without Ethel, Lucy's shenanigans would have befitted a nutcase not a housewife with a penchant for triggering a comedic chain of errors. Without Igor, the extent of Dr. Frankenstein's obsession would have lacked some of the depravity. Without Donkey, Shrek would never have shown how much more of a prince he was than Prince Charming.
Sidekick Rule #3: Intimacy
Mind you, there are a wealth of heroes out there without sidekicks. I happen to think that's a pity. Which heroes of the page or screen do you think would have benefited from a sidekick?