Continuity mistake: At the end of the episode Peggy gives Bobby his birthday cake without any pieces missing from it or marks in the cake. However earlier in the episode, Bobby brings cake for Connie. It's doubtful that there were two identical cakes. You can tell this is the same type of cake because the cream on the top is the same shape and color Bobby brought to Connie.
Continuity mistake: When Bobby runs after Connie, (just before she gets in the truck with Joseph) you can see the front door of the Hill's house is open to the left. Even though in the shot before Connie runs out (and every other episode) the door opens to the right.