Frost and Mullet
After airing episodes from season eleven, channel nine here in Sweden went back to season 1. The contrast is quite significant. I can't help but notice that Frost and Mullet's relationship is considerably more hostile in the early episodes, and overall Mullet's character seems to soften considerably throughout the course of the show. In the beginning he appears downright unpleasant and arrogant, whereass later on he is a lot nicer. He does maintain his pomposity throughout the show, but I felt that later on it's used more light-heartedly than in the beginning. In the episode where Frost hits the pedophile and loses his promotion, Mullet seems to almost like and care about Frost, whereas he plainly loathes him in the first episode. I also thought, though it's besides the point, that DCI Allen was good as an intermidiary office manager, and I was sad to see him go. It allowed Frost to function more as a head street cooper than as a team leader, unlike how the started portraying him from season 6 onwards.
One bad thing about the early episodes, though: too little George :)