The sidekick is not, by definition, the focus of our attention.
They are destined to be overshadowed by their better half, the hero who will save Gotham, solve the uncrackable case or rescue the girl from the bad guys...
But without the sidekick these heroes would often remain too distant, too powerful or just too brilliant for us to ever really love them.
So in steps the earthy, flawed and loyal sidekick to provide the audience with someone to connect to, a character who knows how the world really works to help the hero off tilting at windmills.
Whether it's in countless children's films - think Eddie Murphy's Donkey to Mike Myers's Shrek - or a hundred comic books and cartoons - or high literature from Cervantes to Sterne and Shakespeare to Verne - the sidekick provides the laughs, the pratfall and the focus of our empathy.
Frank Cottrell Boyce talks with those who've created sidekicks, those who've played the parts and those who've studied just how essential these charcters really are to making the fiction seem believable and offer a human face to the often inhuman character supposedly at the centre of the show.