Alessanndra Stanley, in The Vanishing Sidekick, writes:
WHEN Jimmy Fallon showed up on NBC’s “Late Night” last week without a sidekick, it looked like yet another sign that the Ed McMahon era is over; so many talk show hosts work solo that the second-banana position seems almost as obsolete as the foretopman or the Linotype operator. Even the word sounds antiquated: current parlance favors the more “Top Gun”-ian term, wingman.
A real sidekick is something between a friend and a servant — a fervant. Sancho Panza is the exemplar, a paid employee who behaves as if he would gladly serve free, but another is James Boswell, so humbly devoted to his friend Dr. Johnson that he took on the role of amanuensis.
My earliest recollection of sidekick was veteran actor and the perpetually old Gabby Hayes who dutifully played second fiddle to Roy Rogers. Other than a source of comedic relief, Hayes did not seem to serve any other purpose.