Breaking Bad extremely playful on set, with Aaron Paul describing him as "a kid trapped in a man's body". Gilligan originally intended for Aaron Paul's character, Jesse Pinkman, to be killed at the end of "Breaking Bad"s first season in a botched drug deal as a plot device to plague Walter White with guilt. However, Gilligan said by the second episode of the season, he was so impressed with Paul's performance that "it became pretty clear early on that would be a huge, colossal mistake, to kill off Jesse". Donna Nelson, a professor of organic chemistry at the University of Oklahoma, checked
Breaking Bad that he "didn't really give much thought on how well it would sell", stating that he would have given up on the premise since it was "such an odd, dark story" that could have difficulties being pitched to studios. As the series progressed, Gilligan and the writing staff of "Breaking Bad" made Walter increasingly unsympathetic. Gilligan said during the run of the series, "He's going from being a protagonist to an antagonist. We want to make people question who they're pulling for, and why." Cranston said by the fourth season, "I think Walt's figured out it's better to be a