Kids Aging Several Years Between Seasons!

From the Keatons to the Seavers to the rich tapestry of Modern Family, sitcoms have a habit of blithely skipping over the terrible twos and playing fast and loose with the ages of their youngest cast members... This week's trope is kids who age several years between seasons!
Here's what we're watching:

• Family Ties S5 E1 "Be True to Your Preschool"
• Growing Pains S6 E13 "The World According to Chrissie"
• Step by Step S6 E19 "The Facts of Life"
• Modern Family S3 E13 "Little Bo Bleep"