Rachel Dratch was originally supposed to play the role of Jenna DeCarlo. However after creative revisions producers decided to do recast the role and instead have Dratch play different recurring roles throughout the season.
Alec Baldwin's character on '30 Rock' is extremely similar to that which he played in the film Suburban Girl (2007), also a powerful, rich, conservative older man with a beautiful young girlfriend (Sarah Michelle Gellar), an insecure career woman to whom he acts as mentor.
From the first days of the show, executives at GE (which owned NBC at the time) were angry at the many jokes Tina Fey and her writers would make about various corporate actions, and they tried to intercede to either force her to stop doing that or to cancel the show. However, after then-NBC Chairman Jeffrey Zucker was informed of these plans, he let them know two things: the show was to be left alone because the humor "was just jokes" and that he would be angry if he had to deal with the matter again. From that point on, the network ownership left Fey alone to make the show as she wanted to.