This Sunday's episode of Family Guy promises to be a big one. How big? It's-airing-without-commercials big!

In "Send in Stewie, Please," the youngest Griffin spends the episode on a therapist's couch and reveals one of his biggest secrets. It's sure to be important for Family Guy fans as it answers a question we've had about Stewie since the early seasons of the series.

In this exclusive clip of the episode, we see a snippet of Stewie's session with Dr. Cecil Pritchfield, played by guest star Ian McKellan. Cecil attempts to relate to Stewie by telling a story about his past, and ends up reminding us of Stewie in a hilarious way.

If you've already watched the clip then you may be familiar with young Cecil's repeated cries for "mom," because that's exactly the same gag Stewie made famous in the Season 5 premiere "Stewie Loves Lois" and the same joke that I use to really irritate my wife.

Relive that classic here:

Family Guy airs Sunday nights at 9/8c on Fox.