I'll try to keep this short, since there's another matter I'd like to address later on, but one aspect of the series that I've always felt was outstanding is the very subtle, natural way in which many of the characters interact and have conversation, with certain mannerisms and inflections in voice reminding me of people I've seen in everyday life (of course, there are also many characters that are overdrawn and mellow-dramatic; Nora Chandler and Francis Galesko come to mind, as well as others). To me, there seems to be a great deal of improvisation contributing to that sort of natural flow and characterization of speech, and, of course, in certain instances (such as Columbo's interaction with Dexter Paris on the set of Dexter's cooking show) it has been confirmed that improvisation was relied upon heavily to embellish a particular scene.
One scene in the series that stands out to me as possibly being improvised, and with particularly hilarious results, is Columbo's questioning of foreman Fred in "Last Salute to the Commodore". The way Columbo breaks down in almost hysterical laughter in his struggle to understand Fred is, for me, possibly the funniest, most charming scene in the series, where Peter Falk seems to be so genuinely tickled by what's transpiring (intentionally or unintentionally) as the cameras roll (indeed, the whole sequence seems like an outtake, but one that fit so well with Columbo's often amusingly mundane way of gathering information that Patrick McGoohan left it in).
Anyway, does anyone have a favorite scene that gives the impression of being improvised, or a particular actor they feel is good at portraying very natural, nuanced characters?

Now, to address something unrelated, I want to say that I'll be withdrawing from this forum completely, as recent comments have indicated to me that this situation with what I would call a false, dishonest user has simply become untenable. While this "user" may be seen as making legitimate comments as of late, it is very clear to me that he has no sincerity and is making said comments simply to confound and disrupt honest discussion. To legitimize such duplicity, in my view, is a huge mistake and,I feel, is setting an undesirable precedent. I believe that dishonesty is as problematic as incivility in a situation like this, but, granted, dishonesty is more difficult to detect in these cases, and I understand the problem involved there. However, from this point forward it should be overwhelmingly clear the false nature of this "user", should he continue playing make-believe.
Anyway, I'm happy to have had conversation with other fans over the past six months or so, and greatly appreciate the input given in the various topics I have posted!

I'm not always good at spotting these things by a long shot, but to me the whole final scene with Nora Chandler makes it seem like Anne Baxter was allowed to do it exactly the way she wanted to, and I think that worked out very well.

Agreed, Grant! There doesn't appear to be much scripting in this last scene, but, as you mentioned, perhaps she had a bit more freedom than most others have had in the final scenes. I should not, however, that I have read somewhere (the exact location escapes me currently) but that 'Nora' had memory problems and that could, perhaps, be the reason for her unshaken scenes, but this is all conjecture on my part. Any thoughts, Grant?

When Robert Culp is setting up the murder in the episode about the motivational film (I am loosing my memory!) it seems that a lot of what he says, as he imitates an angry/sad boyfriend/street guy, was improvised. That is the scene where he calls up the victim's wife to get her to a Magnolia and Vine. Just an opinion.

in Publish or Perish..the scene where Columbo is eating chili in the fancy restaurant questioning Mariette Hartley and Jacques Aubuchon...
when he goes to leave...he starts to get up and sits back down...stating.."Im having a hard time getting up"...both actors seem to snicker a bit....funny subtle moment

The scene at the end of "Fade into Murder" when Falk and Shatner are fooling around with the video recorder strikes me as an improvisation.

Yes, that makes sense.

I don't know about improvised, but one moment that strikes me as funny is when he's in that hospital waiting room with Milo Janus and he grabs that magazine. It's funny because, what are the odds of someone that infuriated managing to read even one word of the thing? But it also makes sense, because that's just "what you do" in a waiting room. So I wonder whether that was Peter's idea or not.