Susan Mayer's daughter Julie has aged by two years this season.
In the "Previously on Desperate Housewives" intro on episode 1.03 "Pretty Little Picture", the narrator says: "Susan took dating tips from her 12-year-old daughter".
Then in episode 1.10 "Come Back to Me", during a conversation with Mike, Susan says of Julie: "...She just acts so mature, I forget she's thirteen".
And lastly, in episode 1.13 "Your Fault", Susan walks in on Zach kissing Julie and rebukes him saying: "What are you thinking? She's only fourteen".