I'm interested in the gradual development of Miss Pauling.
Originally an almost incidental character in the Team Fortress 2 comics alone, no official model existed for Miss Pauling for the longest time. Her first appearance was in the WAR comic from 2009, two years after the game's release. She is mentioned by name, but you can tell her character isn't nailed down here yet. They probably aren't even sure if they're going to reuse her at this point. The Administrator herself isn't even fully developed yet.
Despite the tangential nature of her character, she made regular appearances in the TF2 comics, always executing the Administrator's will, though not much was really established about her personality or characteristics beyond being hardworking, extremely competent, and very loyal.
Around this time, the fans started making their own models to use her in fanworks, though with not much to go on in regards to her personality, there weren't many people taking an interest in her. The few times she did appear in fanworks, she was often relegated to just being the token girl character.
In 2013, Valve released Ring of Fired, the first of seven full-length Team Fortress 2 comics that would end up being the main source of character development and plot progression for the universe. And Miss Pauling was there as one of the lead characters, although her characterisation was still rather thin in this first issue.
The big moment here is the Love and War update. In 2014, seven years after the game's launch, the short film Expiration Date was released, the 15 minute video supposedly being a pilot for a potential TF2 tv show. That tv show never happened. However, Miss Pauling was one of the lead characters of the video. It finally gave Miss Pauling an official 3D model, which was notably somewhat different looking from her comic appearances up to this point, as well as a canonical voice.
It also established several defining traits to her character: she was extremely neurotic, kind of awkward, a bit silly, and she had a knack for gallows humor. These traits were heightened with the following Gun Mettle and Jungle Inferno updates, which gave her a bunch of voice lines where she talked to the player characters and let her kookier side show.
These traits would make it back into her characterisation in the comics going forward, finally reaching Maximum Pauling. She became the true Main Character of the TF2 comics, usually being the main perspective character, as well as being the character with the heaviest choices to make as the plot reaches its climax.
While Miss Pauling still to this day doesn't physically appear in the Team Fortress 2 videogame, she has become one of the most important characters of its surrounding universe, and you'd be hard pressed to find a fan who doesn't really like her. It's been fun to watch her develop from an incidental lore character to the unofficial tenth member of the main cast. I'm a huge fan of her.