It's the episode where Maggie ends up with Burns's long lost teddy bear (a bear she happens to be playing with in this same scene while Homer is watching TV).
Shot in the dark: Is it the one where Maggie keeps trying to kill Homer because she saw Itchy and Scratchy do it? Marge puts on something more wholesome for her, and it's this Barney expy?
Also, the answer is seven (/c/ConfidentlyIncorrect)