In the credits for the 100th Episode Special, one of the "Also Starring" actors was Lacey Chabert.
For those of you who don't know, in the first season, Lacey voiced Meg (that's her as Meg saying "Oh, No!" when Peter is sentenced to two years in prison - remember, this is the special that came before "Stewie Kills Lois", not the episode itself), but for whatever reason, she was not credited (somebody posted something recently claiming that she demanded that her credit be removed because of her Christian beliefs, but there's no evidence that the source that was quoted even exists). Either somebody was asleep at the switch or somebody has decided to let bygones be bygones - but in that case, why wasn't she given a full "Starring" credit?
-- Don