episode creation, "I'm sort of the brain. Brad's sort of the heart. Ian's sort of the funny bone", which Brennan says "is true in a lot of ways". Some of the characters are written more by one writer than by the others. Brennan writes most of Sue's material, and Falchuk frequently writes the scenes between Kurt and Burt Hummel, though Murphy contributes a great deal to Kurt. Starting with season three, a writing staff of six was hired: Ali Adler, Roberto Aguirre-Sacasa, Marti Noxon, Michael Hitchcock, Matt Hodgson and Ross Maxwell. The season's fourth episode, "Pot o' Gold", was written by Adler, the first not credited to the show's three creators. Adler and Noxon did not return for the show's fourth season and instead House writers Russel Friend and Garrett Lerner, and Stacy Traub were hired. Music and choreography The series features numerous song covers sung onscreen by the characters. Ryan Murphy was responsible for selecting all of the songs used, and has said that he strove to maintain a balance between chart hits and show tunes: "I want there to be something for everybody in every episode. That's a tricky mix, but that's very important—the balancing of that." According to Murphy, the song choices are integral to script development, "Each episode has a theme at its core. After I write the script, I will choose songs that help to move the story along." In a 2010 interview with Allison Kugel, Chris Colfer noted that "there have been a couple of times when I have gone to Ryan Murphy (Glee creator) and told him a couple of things that have happened to me, and then he writes it into the show. Or he'll ask me what song I would want to sing, in this situation or in that situation. I don't think any of us directly try to give input on the character or on the storyline, but they definitely steal things from us." For the second season, a shift toward using more Top 40 songs was seen, in an effort to appeal more to the 18–49 demographic. Murphy was surprised at the ease with which use of songs was approved by the record labels approached, and explained: "I think the key to it is they loved the tone of it. They loved that this show was about optimism and young kids, for the most part, reinterpreting their classics for