Kent appears on the show pretty much fully formed, what we see in Krusty Gets Busted is not that different from what we will see for the next 30+ years, in terms of appearance, demeanour and voice.

This is because Kent is the sort of character that is meant as a stand-in to represent an entire aspect the show wishes to explore - in this case, the American news media machine. The writers knew the commentary they wanted to make about the news, and the news hasn't changed dramatically since then.
In 1990 America was still in the early days of round the clock news coverage. CNN launched their first 24 hour news channel in 1980 and things escalated for there. It is likely that news channels were always competing for viewership and advertising dollars, but in the lifespan of The Simpsons, this has become more blatant - and Kent is at the heart of it. He relies on sensationalist journalism and dubious fact-checking to boost his celebrity status, and like many figures in Springfield uses his corrupt position to meet his own wants and needs.
This may seem like a common way to portray the news, especially in comedy, but I am struggling to think of an earlier example of this kind of character. Unless Kermit the Frog was taking back payments in his reporter segments on Sesame Street (we can't rule it out), this depiction of the media as something you can't necessarily trust was relatively new.
We are offered some insight into Kent's home life. He is/was married to the weatherlady (we will see her, but not for a while), and has at least three children, only one of whom ever appears. Like many characters, he is defined by the role he represents in the show, to the point where even when he is not working he will speak in a news anchor cadence.
I believe that Kent Brockman is the final major character we will encounter in season one - by "major" I mean the sort of character that an average Joe on the street is likely to be able to name. We still have a fair few characters to cover (this isn't even the last episode of the season), but our recognisable cast of Springfieldians is starting to come together.
This post is part of my "Every Simpsons Character Ever" series. For a list of my rules in this project, click here.