I think like Felicity, they made a small amount prior to the debut year, but these were not released to the public until the debut year. So some of the first Addys are actually tagged 1986 on their dresses and drawers and are slightly different (apparently) from some of the others released during the same year.

My Felicity was bought from PC on her debut year in 1991 but her shift and gown is tagged 1986.

Hope that helps!