In "Dammit Janet", Brian and Stewie have caught one another supposedly in love, while thinking they were keeping it a secret. Both times this happened, the character who caught the other is standing in a doorway, eating an apple while teasing the first character.
While watching the news special about sex, Lois mentions it's nice seeing something other than violence on tv. This is a reference to the theme song.
Brian is 7 years old in this episode.
While Peter is attempting to potty train Stewie he suggests just giving him a beer. Stewie sarcastically comments they might as well light up a doobie and watch porn to which Peter replies "...yeah?". This means Peter can understand Stewie.
In terms of production order, this is the first episode where Mila Kunis voices Meg Griffin, replacing Lacey Chabert. However, Chabert's Meg would still be heard after this in some holdovers from the season 1 production order.