During the 1950's run of 'Dragnet', Lt. Joe Friday (played by Jack Webb) was partnered with several cops:
Sgt. Ben Romero (played by Barton Yarborough)
Sgt. Ed Jacobs (played by Barney Phillips)
Officer Frank Smith (played first by Herbert Ellis and then by Ben Alexander) But that isn't exactly recasting when it comes to Officer Frank Smith. They weren't the same police detective, but two different cops who happened to have the same name.
In a police department as large as the one in Los Angeles, there was bound to be several policemen who had the same name. And you have to admit "Frank Smith" is rather common. (In Toobworld, the LAPD even had three lieutenants all by the name of "Columbo".)
That Joe Friday got saddled with two Frank Smiths as his partner, one right after the other, is typical of Toobworld "coincidence". But it's always better to go with the simplest splainin, rather than drum up some reason for the original Frank Smith to be replaced by an alien imposter or quantum leaper.....
And I don't think either one of them could be related to the crime syndicate boss of Port Charles, NY, who was also named Frank Smith. Now THAT's a guy who had to be replaced by a quantum leaper from the future! BCnU!