Why does a hero need a sidekick? I think we can sum this up PERFECTLY by going to the first story to introduce a sidekick: The Creation
Genesis Chapter 2
22 And the rib, which the Lord God had taken from man, made he a woman, and brought her unto the man.
Eve, our first sidekick ever (and this is true no matter what Creation myth you are reading, the woman is always created after the man), is created to be an helpmeet. In the Bible (KJV), “meet” simply means “suitable, fitting, and proper.” The word help is pretty simple and straight forward.
When God created Eve, he was creating a ‘suitable and proper helper’ for Adam. This description we can apply almost universally for sidekicks. They are always both a compliment to the hero and the necessary support for them. This support may seem primarily an emotional support, but it is nevertheless a necessary support system for the hero.
Like Eve for Adam, it is clear to us that a hero is not ‘complete’ or whole without his sidekick. Though sidekick may appear to be, or may in fact be, somewhat weaker than the hero, have comparably different skills, or are at a lower level of completion of the same skills, what skills and strengths they do have are complimentary to the hero and aid him in his quests whether they be lifelong, daily or a single event. The weaknesses of the hero, his need for companionship and support, allow him to accept his sidekick–his help meet–without complaint. He also accepts responsibility for them.
When Eve was tempted by the serpent and fell to sin, Adam did not abandon her to her fate outside of Eden, but joined her in it, knowing it was as much his responsibility to support his help meet (read: sidekick) as it was for her to support him. He knew continuing his life in the Garden without her was a choice that was not heroic. His life, though perfect and sinless, lacked the same meaning and purpose when alone. The choice to be without her was therefore unacceptable.
Though the function of a sidekick isn’t necessarily to be heroic–at least not in the same way that the hero is–we expect from them the same sort of positive actions. Because they are a sidekick, we accept from them their mistakes. It makes them the easier part of the superduo to connect to and relate with. We never seem to blame them for forcing the hero in difficult circumstances (Eve forcing Adam to choose between life with her in the world where he would be forced to toil for his food and the Garden where life was perfect). We accept it as a consequence of having a sidekick–a helpmeet.
There are, of course, heroes without sidekicks, but they always seem sterner, darker and aloof. Batman without Robin is “The Dark Knight.” Frodo without Sam would have certainly died. And Superman without Lois Lane is a lot less interesting.
No matter who the hero is, or who the individual is, we all realize that a life without that help meet is not as ‘complete’ as one with. This is the understanding that makes sidekicks so valuable and so valued.