Other mistake: The scene where Alice is giving Tiger a bath was the same one used in "Katchoo Katchoo", albeit with some audio dubbing thrown in, like when Alice complains about the floor getting wet. (00:04:05)
Other mistake: A final contest is given for control of "green stamps" with all the kids building a "House of Cards." Whomever causes the cards to fall will be the losers. All is going well until Tiger comes in and knocks into Greg and causes him to bump the table and knock over the cards. If you watch closely at the end of the scene, when all the dialog is finished, you can see Mike trying to knock down a few remaining cards. However they keep popping up. Probably due to the fact that the cards were glued together to make it easier for the kids to build upon.
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.