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).
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.
Vivian: Philip, when I met you, you were into James Brown.
Will: He liked James Brown?
Vivian: Even wore his hair like him.
Will: He had hair?
Papa's Got a Brand-New Excuse - S4-E24
Trivia: Ben Vereen, who played Will's dad Lou, admitted that as soon as he walked out of camera range, he immediately broke down into tears.
Answer: He's coming back from his vacation in Philadelphia.