Liam Neeson told the writers he would say and do whatever they came up for his role on the "Fighting Irish" episode. The only time he went against this was with the line "I've been a world famous tough guy since I was 56" because it referred to his work on "Taken" and Neeson was 55 when that was filmed. The change was immediately made.
The 250th episode of the series.
Brian, Meg and Chris appear but don't have any lines.
In the "cutaway" scene where there is a family of woodchucks; when the father woodchuck is explaining to his son that leaving the traditional wood chucking business to become a doctor is not a good idea; what he says to his son is based on the tongue twister "how much wood can a woodchuck chuck if a woodchuck could chuck wood."