Continuity mistake: The number and position of the darts on the dartboard changes between shots. (00:06:45)
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)
Other mistake: Just after Bobby and Cindy get lost, there are shots showing Mike and Carol calling for them. A couple of minutes later the same shots are shown again, but this time they're flipped. (00:22:00)
Plot hole: The Bradys and Alice run a relay through the amusement park to get the sketches to Mike at the manager's office. They locate another person to pass the cylinder off to when they get too tired to run. But they all arrive together seconds after Carol gives the sketches to Mike. (00:19:15)
Continuity mistake: Through the course of the episode, Greg has a spot in his eyebrow over his right eye that switches from shaven to unshaven.
Continuity mistake: The horse figurine and telephone on the table next to Greg are not in the same positions from shot to shot. (00:07:15)
Plot hole: When Mike was at the meeting and pulled out the Yogi Bear poster, he said he could find the other cylinder, and was told by one of the other men that they had to catch a plane in 30 minutes. After that, he had to find Jan, and then Jan and Marcia had time to go on about 4 rides and then find the sketches and then start their run across the park. There is no way all of that could have been done in less than 30 minutes.
Character mistake: While they're dancing and practising in the garage Marsha says "come on Chris", when she should have said Peter.
Is There a Doctor in the House? - S1-E13
Other mistake: At the end of the episode, when they were looking at the chart they created, and Alice was found to add the measles, you see Mike Brady adding the word "Alice." But the kids and Tiger all had columns, but he is adding her as an extra row, which was for the different illnesses, to suggest that Alice was an illness instead of a person having the illness.
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)
Confessions, Confessions - S2-E12
Continuity mistake: The vase broken by the ball is obviously not the same one dropped by Carol at the end of the episode. The first one was thicker and darker. (00:02:15 - 00:24:05)
Top Secret - S5-E19
Revealing mistake: Bobby and Oliver are building a house of cards on a small platform sitting on the table when all of a sudden the house of cards collapses. The reason: the platform moves by itself. Clearly it was manipulated off-screen somehow. (00:01:20)
Top Secret - S5-E19
Continuity mistake: The amount of talcum powder in Bobby's and Oliver's hair increases from one shot to the next. (00:14:35)
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)
Confessions, Confessions - S2-E12
Visible crew/equipment: The shadow of what appears to be a moving camera can be seen moving across the pieces of broken vase. (00:02:35)
Audio problem: Tiger is heard barking as he runs down the stairs, but it's obvious the dog isn't barking at all. (00:06:05)
Kitty Karry-All is Missing - S1-E7
Continuity mistake: As Bobby empties his pockets in search of his kazoo, he piles the contents on a nearby table. In a long shot, several of the toys (most noticeably a green plastic paddle) disappear, only to reappear when Cindy is leaving the room. (00:18:10)
Continuity mistake: When Marcia is sitting on the couch talking with Davy, the small beige pillow behind her is either up on the back of the couch or much further down depending on the shot. (00:23:20)
Continuity mistake: The amount of cookies in the cookie jar Bobby is holding increases from one shot to the next. (00:10:20)
Continuity mistake: When Zaccariah steals the last piece of fried chicken off the plate, the plate is left completely clean, yet when Alice goes to get the piece a few seconds later, there's a sizable grease stain on the plate. (00:14:05)
Answer: There were several episodes throughout the run of the show where Marcia was infatuated with a guy she went to school with. This bracelet could have been a gift from her then-boyfriend; as such, she would not want to take it off, as a sign of loyalty. A stupid thing to do, of course, but it's not a mistake for a character simply to be dumb.
Matty Blast