Reggie Mantle is a major supporting character in Riverdale, having a role across all seven seasons of the show. Originally created back in 1942, Reggie served as the rival to Archie Andrews in the Archie Comics, and the two would essentially be frenemies for a large portion of their comic book history. When it comes to the live-action Riverdale adaption that began in 2017, the show leaned on that rivalry, with Reggie largely acting as an antagonistic force to Archie through the first season.

https://screenrant.com/reggie-riverdale-recasting-explained/