sidekick

1. (informal) An assistant to another person, especially to a superior or more important person.Examples: "In the abstract, Stuhlbarg’s twinkly-eyed sidekick suggests Joe Pesci in Lethal Weapon 2 by way of late-period Robin Williams with an alien twist, but Stuhlbarg makes a character that easily could have come across as precious into a surprisingly palatable, even charming man."; "If representation and recruitment is an objective, self-styled mavericks like Kelly and his Queensland sidekick George Christensen have some utility."; "Elon Musk, Mr. Trump’s new sidekick, shared on his social media platform X an NBC News video of Pennsylvania Democratic Sen. John Fetterman, who suggested the Gaetz pick was a strategic move to upset Democrats."informal

2. (authorship, figuratively) In literature, theatre, etc., a good foil of the protagonist, a character who helps emphasize the traits of the main character.Examples: "So even though he had – no question – the best lines in Friends, he was never what he would have been in an earlier era: the sidekick."figuratively