Then there's the famous case of Bewitched, when Darwin-- I mean, Darrin Stephens changed from Dick York to Dick Sargent (due to York's health problems), and not even Samantha noticed the difference.
But that's a different phenomenon altogether. That's just recasting a single character. What I'm talking about are instances where one character was nominally replaced by a different character with a different name, yet the "new" character was written identically to the old one.
Actors work from the script, character descriptions or template they recieve. From every analysis of the effect of "The Cage," once Hunter was not an option, Roddenberry did not wish to clone Pike, as he was not appealing enough--certainly not for a regular series lead. Kirk and Pike were anything other than interchangable personalities no matter the perfomer.
We've been through this already earlier in the thread. The differences in the characters emerged in the actors' performances, and over time, the writers began writing Kirk to reflect Shatner's performance. But we're talking about how Kirk was written in the second pilot and early first season. The Kirk who in "The Corbomite Maneuver" was as uncomfortable with a female yeoman as Pike was. Who in "Mudd's Women" was so ultra-serious and driven that he was the only human male in the crew who wasn't affected by the titular ladies. Who in "The Naked Time" was yearning for a simpler life free from the burdens of command exactly as Pike was. Who in "Balance of Terror" needed a pep talk from his doctor exactly as Pike did. (And McCoy was exactly the same character as Boyce too -- let's not forget that Roddenberry wanted DeForest Kelley as the doctor from the beginning.)
Remember what I said about Maverick
. Every script was written with the assumption that James Garner would be playing it. There was nothing to distinguish the scripts that went to Garner, Jack Kelly, and Roger Moore except for scheduling; the hero was written identically in every case. And yet the three actors were perceived as three distinct characters -- Bret more comedic, Bart more serious, Beau more suave and gentlemanly -- based entirely on performance, not script. So you're giving actor interpretation far too little credit. The same script performed by two different actors can produce two very different characterizations.
For another example, watch different actors' interpretations of Shakespeare, or different performances of other plays. A few years back I watched two different versions of Hamlet
, the 1980 Derek Jacobi one and the more recent David Tennant one. Their Ophelias were delivering the same lines but couldn't have been more different in personality -- Lalla Ward's 1980 Ophelia was so weepy and pathetic that it was a relief when she went mad and finally seemed to be having some fun, while Mariah Gale's 2009 version was so strong, assertive, and canny that I wondered if she was faking her madness as a ploy just as Hamlet did. Not to mention that Sir Patrick Stewart played King Claudius in both versions, yet even the same
actor delivering the same lines created two diametrically opposite characterizations 29 years apart: The younger Stewart rushed through Claudius's lines and gave a superficial, shallow performance, while the more mature Stewart gave him so much depth and gravitas that you admired him even though he was the villain.
So really, there's far more to it than just what's scripted. The actor can completely transform what's on the page.
To his credit, Shatner picked up on the warmth / humor, but that was in the WNMHGB script for Kirk.
was there, but it was there in "The Cage" too. Imagine Shatner and Kelley having the exchange about doctors and bartenders.
Interchangeable personalities occured to some degree on M*A*S*H, where uptight, snobby and judgemental Frank Burns was replaced by uptight, snobby and judgemental Charles Winchester--essentially born of the same need of an easily targeted foil for the leadback series leads.
Wow, you're just incredibly off the mark there. The whole reason the producers replaced Frank was because the show had grown more sophisticated, the characters more nuanced, but Frank had become an irredeemable caricature of incompetence and just didn't fit the show anymore. So they replaced him with a more three-dimensional character who worked for what the show had become. Charles was superficially an obnoxious foil like Frank, but he was supercompetent in contrast to Frank's ineptitude, he wasn't lovestruck over Maj. Houlihan the way Frank had been, he was a culture snob rather than a petty bigot like Frank, and though he had his rivalries with the other doctors, he also had admirable qualities and sometimes found himself allied with the others in a just cause.
is one of the leading counterexamples to the pattern of identical replacements, because all its replacement leads were quite distinct in personality from their predecessors. Trapper John was a womanizer like Hawkeye, but BJ was a devoted family man. Blake was a drafted civilian who was uneasy with authority and would've been lost without Radar, but Potter was a career military man and proud of it. And when Radar left, they didn't bring in an equivalent character but had the very different Klinger take over his job. Not to mention how much the leads who stayed
changed over the years, with Hawkeye becoming more serious and thoughtful, Margaret becoming more nuanced and sympathetic, etc.