Other mistake: When the frog jumps on the pizza (during Greg and Rachel's date), the gooey cheese mess resembles more superimposed tacky glue than actual melted cheese.
Fright Night - S4-E6
Continuity mistake: When Jan, Marcia, and Cindy search the boys' room Cindy finds the slide projector under Greg's bed, and when Marcia holds up the transparency slide with the "ghost" image, the close-up of the slide presents two problems. First, the "ghost" is horizontal in the wide shots, but is vertical in the close-ups, and second, the fingers holding the slide in the close-up do not belong to Marcia.
Continuity mistake: In "Our Son, the Man", Greg wants his own room. One night, while in bed, Mike and Carol discuss their options. Carol says, "How about the attic?" Mike responds with, "That would be fine if Greg were only two and a half feet tall." Later, they give Greg the den for a while. However, in "A Room at the Top", after cleaning out the attic, which was now full size, both Greg and Marcia want it for their own private room.
Character mistake: When the Brady kids are practicing for the talent show, instead of saying, "Come on, Pete," Marcia says, "Come on Chris," which is the actor playing Peter's real name (Christopher Knight). (00:14:30)
Career Fever - S4-E9
Plot hole: Peter thinks he has a fatal disease. The parents realise two pages stuck together and he went from page 95 to 98 mistakenly. However, Mike first read about the actual fatal disease info on page 97, and then Carol read about what Peter actually had on page 96 (poison ivy). If Peter read only 95 and 98, there would be no way of Peter to know his disease was fatal since that was printed on page 97.
Continuity mistake: When Marcia is cheering in the backyard, her locket tucks itself into her shirt when she finishes.
Fright Night - S4-E6
Continuity mistake: Mr. Brady places the bust on the half-wall behind the couch. When Alice swings her purse at it, it shatters immediately, but when the lights are turned on, it looks like all of the pieces are in the middle of the floor between the couch and chair.
The Great Earring Caper - S4-E20
Continuity mistake: During the kids' ping pong game in the backyard, there is something white near Jan's feet that appears to be a spare ball. But in the very next shot, it's gone. (00:12:40)
Everyone Can't Be George Washington - S4-E12
Continuity mistake: When Jan's in the backyard checking on the cloud and moon set decorations being painted by Marcia and Cindy, there's less "dark and gloomy" paint actually painted on the cloud after Cindy stands up with the smiley moon. (00:06:20)
Visible crew/equipment: After Bobby tells Alice that he can't pass Jan the potato chips because he's "not here", when Greg walks in and Bobby tells Alice that Greg's "not here either" we can see the tape mark on the floor behind Jan.
Continuity mistake: While the kids are practising the potato sack race as Jan watches from the sidelines, when Marcia steps into her sack and hops away there's a large color image on the front of the sack, but when she reaches Peter, then turns and heads back the image has vanished - it's not on either side, then it reappears when she's back with Bobby. Additionally, when Cindy hops in the sack that Greg was in, the sack is ripped at the bottom and Cindy's feet are on the grass, but when Cindy reaches Peter the bottom of her sack is perfectly intact.
Audio problem: In the scene where Mike comes home and Carol has ruined his golf club, you hear a door open and close, with a latch/doorknob. She hears it and knows he is home. But he comes in the back door, which was a sliding (glass) door. (00:20:00)
Continuity mistake: The amount of garbage in the abandoned house - especially in front of the fireplace - increases from one shot to the next. (00:16:20)
Character mistake: While they're dancing and practising in the garage Marsha says "come on Chris", when she should have said Peter.
You Can't Win 'Em All - S4-E22
Continuity mistake: At the start, when Cindy walks into the kitchen she sets her books down on the counter with the book's binding facing the sink, but in the closeup the book's binding now faces the opposite way, toward the stove. Additionally, the grocery bag which was on the counter right beside Carol, has been moved for the closeup so Carol is in full view, but the bag is now at the very edge of the counter near the stove, which is pretty odd since there's not enough counter there to actually hold the full grocery bag (presumably something else supported the bag off camera). (00:01:30)
You Can't Win 'Em All - S4-E22
Continuity mistake: What appears to be a carton of eggs is sticking out of one of the grocery bags in some shots, but not in others. (00:15:00)
Audio problem: Alice's comment to the girls while handing them their books was obviously dubbed; there's an unusual echo quality in the sound. (00:03:05)
Continuity mistake: When Greg comes home after Jennifer gives him her number, Greg is seen entering the house in the living room. Then a few seconds later he is seen entering the other side of the kitchen.
Continuity mistake: The CLOSED sign behind Sam in the butcher shop keeps alternating between being tilted to the left and tilted to the right. (00:14:45)
You Can't Win 'Em All - S4-E22
Revealing mistake: When Cindy and her parents get home after the television show, just as Carol and Mike walk down the steps the set's unfinished wood can be seen at the edge of the steps, at the bottom right corner of the screen. (00:22:40)
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.