UPDATED with more news: Fox said today that it will air a first-ever extended-length Family Guy episode in the spring that will feature limited commercial interruptions. Details of the March 11 episode, titled “Send in Stewie, Please,” were unveiled today during Fox’s executive session on Day 1 of the TCA winter press tour in Pasadena.

In the episode, Stewie gets sent to the office of his school’s child psychologist, Dr. Cecil Pritchfield (Ian McKellen), after pushing one of his classmates. During the session, Stewie experiences a series of personal and emotional revelations about himself.

The news comes as Fox readies the 300th episode of Seth MacFarlane‘s animated flagship, now in its 15th season. That milestone episode, “Dog Bites Bear,” is set to air January 14.

Also today, following a live-read session of the show, it was announced that Amanda Seyfried would guest this season on a future episode. She will voice Ellie, a dog that Brian dates.

Family Guy, from 20th Century Fox Television, airs at 9 PM Sundays.