Actor goes from second banana (or other side role) to lead

Again, switching back and forth between two main characters isn’t quite the same thing. I’d considered this case, too, but dismissed it as not quite the same thing.

The supposed case of Anthony Quinn and Laurence Olivier switching roles in the Broadway production of Becket similarly doesn’t count. I addition to which, it apparently didn’t really happen.

I see your point; but, well, if one of them really did get top billing, and the other got second billing, then I figured: who am I to argue?

I think this is a perfect match. Although it probably means more in the UK.

British actor Ray Winstone (Sexy Beast, one of the Indiana Jones films) had an incredibly minor role (“second thug”) in a single episode of terrific UK TV Police Drama The Sweeney. That was 1976 and one of his first acting jobs.

In 2012 a rather feeble cinema film reboot of The Sweeney starred Winstone now as the lead character (in both the film and original TV series) Jack Regan.

TCMF-2L

Another from Doctor Who: Freema Agyeman played the small role of Adeola in “Army of Ghost” and later became the companion Martha Jones. They explained it by saying Adeola was Martha’s cousin.

Bodine, please. They’re hill folk, not Cajuns.

Lewis was an underling to Inspector Morris before becoming an Inspector in his own right.

Just as Morse is an underling to Thursday in Endeavour (although here Thursday is the subsidiary character).

I just hope we never get a Hathaway.

They were thinking about doing a series with Inspector Hathaway in the lead but changed their minds.

The most infamous case was the early Fox sitcom Duet. Mary Page Keller and Matthew Laurance played a dating, then married, couple. Alison LaPlaca played her yuppie best friend.

After 54 episodes, Duet was cancelled. LaPlaca’s character was the most popular on the show, so they spun her off into her own series, Open House. Keller’s character came too, quitting her catering job that she had on the Duet show so she could be LaPlaca’s sidekick. I don’t know if her husband (Laurance) or child (!) were ever mentioned on Open House. It was a very weird transition. Open House lasted for 24 episodes. LaPlaca later got sort of a rep as a female Ted McGinley, aka showkiller. This is the classic example.

a reminder, folks. The OP wants examples of actors who played minor characters, who returned as major role, different character, in the same series, or movie remake.

He doesn’t want minor characters that became more important, or who got their own spin-offs.

John Mahoney had a small role, a character called Sy Flembeck, in an episode of Cheers, then returned as Frasier’s father. Different characters, moved from a small role to a large one.

Patrick Newell played two different small roles in The Avengers before returning as Steed’s boss. Different characters, moved from two small roles to a large one.

Things like that.

In addition to narrating over the theme sequence, Roger Davis played a gunfighter in one episode of Alias Smith & Jones.

Following the death of Pete Duel, Davis took over his lead role as Hannibal Hayes.

Similar to this, Lance Barber had a role in one episode of “The Big Bang Theory” as a former bully who used to pick on Leonard in high school (and who, as it turned out, was still a bully).

He now has a much bigger role as Sheldon Cooper’s dad on the spin-off “Young Sheldon”.

Franz did this as Supowicz in NYPD Blue. He started out as the bigoted and hateable number two guy to David Caruso’s Detective Kelly, then grew into the gruff-but-lovable backbone of the squad, then ultimately the leader of the squad.

But he was the same character all along the way, so not what the OP was looking for…

Patrick Stewart went from playing Guinevere’s father in Excalibur (1981)
…to Merlin in The Kid who would be King (2019), although the latter wasn’t a top-banana role.

NCIS - Tim McGee joined the cast in Season 2. Playing the socially awkward computer geek. He was 3rd banana behind Gibbs and Tony. Sometimes McGee is 4th banana when Ziva was prominently featured.

McGee is currently team leader. Gibbs, Tony and Ziva are gone.

Sean Murray plays McGee. His step father is Donald P Bellisario, the Executive producer of NCIS and other hit shows.

Don Knotts went from sidekick Barney Fife on The Andy Griffith Show to starring in several movies. The Ghost and Mr Chicken, The Incredible Mr. Limpet, The Reluctant Astronaut, The Shakiest Gun in the West and The Love God. All made for Universal Pictures.

Close enough. That’s a pretty good example.

Just remembered this one in time for Halloween.

Klaus Kinski played Renfield in 1970’s Count Dracula with Christopher Lee as the Count.
9 years later he played Count Dracula in Werner Herzog’s Nosferatu, the Vampyre

Sean Murray started sometime during season 1.