Visible crew/equipment: When the shelf falls in the store, you can see the rope attached to the top of the shelving unit being pulled from off-screen triggering the collapse of the shelving unit, it was not the girl's weight that made it tip.
Other mistake: Carol grabs a pot holder with her right hand and removes a small cake from the oven. The cake pan is obviously not hot. It starts to tip and Carol steadies it by placing her bare left hand on the underside of the pan.
Continuity mistake: The bottles of pop on the kitchen table keep changing position from shot to shot. (00:22:55)
Answer: Much trivia has been written about "The Brady Bunch, " including the various interrelationships and dynamics among the members of the cast. For example, much has been written about why Robert Reed's Mike Brady did not appear in a couple of episodes, including the series finale, due to rancorous creative and artistic differences with series creator, Sherwood Schwartz. However, in contrast, I have never run across any reasons given why a particular child did not appear in specific episodes - only that the episodes were missed. This suggests the causes were likely unexceptional, such as illness, injuries, vacations, or real-life family obligations.
Michael Albert
Although those options ARE possible reasons, it just seems a bit ironic that this happened all in Season 2 ONLY and within a short amount of nearly consecutive episodes. Never happened during the other 5 years of the show at all.