Check out the following clip from Supernatural.
If the actors weren't there, if all you had was a script with the character names blacked out, you still be able to tell the difference between Sam, Dean, Castiel, Bobby, Adam/Michael, Crawley, Eve, Charlie, etc.
Because each character is unique. Three-dimensional. And they each have their own verbal tics and cadence.
Here's an exercise for beginner and advanced writers. Get a partner. Each of you record a show that
the other partner has not seen, or at most, caught three or fewer episodes. (You can cheat and pick out a clip on YouTube like I did.)
Write down the dialogue for one scene, but with altered tags. Example: Dean would Character 1. Castial would be Charater 2. And so on. Or use highlighters, i.e. Dean would be blue, Castiel yellow, etc.
Trade pages and read aloud to each other. Every human (and angel) speaks with a particular rhythm. From the rhythm, word choice, inflection, and so on, write down your impressions of each character. Then trade back and see how close you were. In fact, I suggest watching the entire episode that your example dialogue came from to see the connection.
Study and apply to your characters
Why is this important?
Because you want your readers to feel that you characters are real. And because it's always hysterically funny when an angel mangles a human insult.
On Not Writing
4 hours ago