Why did they turn the bobby character into a bratty kid by the end of the shows run he was a trouble maker ?

http://www.youtube.com/watch?v=7RGow_trmiU
http://www.youtube.com/watch?v=CyOqEimpca8
http://www.youtube.com/watch?v=Gs0Pqm7TA6U

Why did they turn the bobby character into a bratty kid by the end of the shows run he was a trouble maker ?

http://www.youtube.com/watch?v=7RGow_trmiU
http://www.youtube.com/watch?v=CyOqEimpca8
http://www.youtube.com/watch?v=Gs0Pqm7TA6U
A lot of boys go through a bratty stage while they're growing up. Peter did. Remember when his "hobby' was hiding a tape recorder around the house to record family members conversations? Near the end of the serie Bobby was reaching the right age to go throughthis stage.

It seemed like greg was the only mature one of the group for the 5 year run since he was older.

http://www.youtube.com/watch?v=F36tONrZeHs
http://www.youtube.com/watch?v=GtVahVom_Hk
http://www.youtube.com/watch?v=1RvVuI6hbhk