Factual error: In the park, Stewie and Brian are playing the "water pipes" like a xylophone. Trouble is, in order to get the tones they were playing, the glasses should have had different levels of water in them. If you look closely, all the glasses have the same level of water.
Factual error: Brian is sitting on the couch smoking weed. Joe knocks on the door and Brian just waves the smoke from the air. Joe is there to give Brian a drug test and says nothing about smelling weed in the air. There's no possible way he didn't smell it! You can't just wave your hand and get rid of the smell.
Answer: Lacey Chabert was the actress who originally voiced Meg in early episodes. She left of her own accord due to being in school and other acting work; Seth MacFarlane has stated there was no tension with her leaving, but it makes for a handy joke for the show.
Jon Sandys ★