Continuity mistake: The last line of Alice's recipe, written on the chalkboard, changes from "3 egg yolk" to "3 egg yolks" and back again. (00:06:15)
Continuity mistake: In the photo of the football reception, the enlarged photo is not from the original. The receiver's legs are in a different position. (00:22:35 - 00:23:20)
Continuity mistake: The football diagram that Greg draws on the chalkboard changes from shot to shot. (00:07:00)
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.