Continuity mistake: When Bobby is driving the golf cart, he is alone. However, when he stops the cart to invite a neighbour (also in a cart) to his party, you can see feet and knees of someone sitting in the rear of the cart.
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: Whilst Joseph is fixing his bike, there is a green mat next to it. As he starts to ride the bike the mat has now disappeared.
Other mistake: After Hank & Peggy pick Bobby up from the airport you can see part of the clouds through the windshield. One of the clouds you can see stays in the exact same spot whilst they are driving along the main road in the back windshield. It is a cloud because of the distinct color. It also couldn't be a sticker as you can see when they park the car at the restaurant there are no marks on the windshield.
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.
