Continuity mistake: When Phil is telling Geoffrey about his day at work he takes an aspirin and drinks the water. The glass of water is almost gone. But if you look closely a couple of shots later the glass is full of water again.
Plot hole: Ashley says she is 9; later in that season, in "Just Infatuation," Phil says she is almost 12. Will is 17 for the first two seasons, and 18 in season three. Nicky Banks grows from baby to preschooler between seasons four and five (though this was humorously addressed).
Revealing mistake: When Phil is looking for Will who is in Ashley's room he slams one door shut and the set wall can be seen to wobble. (00:11:00)
Character mistake: When Geoffrey serves tea after his sassy cough at Vivian's sentence about High Tea not being a sacred institution, the actor messes up when it's time to actually serve tea, with a napkin getting caught in the teacup saucer. Granted, accidents do happen, but it's quite uncharacteristic for the perfect butler Geoffrey is portrayed to be, and simply a flub by Joseph Marcell. (00:17:45)
Continuity mistake: When Ashley shows Will her weekly schedule, her hand is towards the middle of the upper roll of the parchment, but in the reverse shot where the calendar can be read, her hand is at the top right corner. (00:03:30)
Answer: He believed he was asserting his independence and individuality, not giving in to the conformist rich society. Movie quote, "I don't act this way to change the world. I act this way, so the godamn world doesn't change me."