Other mistake: Near the end, when the police chief "sees" the fake UFO, he picks up the phone and dials 3 numbers and immediately speaks to said caller instead of the operator or asking for an extension.
Audio problem: There's a very echoey essence all throughout the episode like they're shooting in a cave.
Continuity mistake: Mike has just pulled into the driveway and honked, as the family waits excitedly for him to come in and share his great news. Then, a second later, he's coming around the counter to greet everyone, instead of a car door or patio shutting.
Answer: I think I remember that episode - but, more importantly, my mother always told me (and my siblings) to stop jumping/ stomping, running in the kitchen, and opening the oven door when a cake was baking... because these could make the cake fall. I believed my mother... and I, as a child, also caused a few "fallen cakes" because I didn't quite always listen (right away, anyway). I'm sure Alice's fallen cake episode was exaggerated, but cakes really CAN fall from stomps and opening the oven door too soon. Usually, it has something to do with the baking powder and how the air bubbles change during the baking process. Doing something that might cause the oven and cake inside to move/shake can suddenly change the air bubbles inside the cake and cause a collapse. I don't know all factors that have to occur for a cake to fall (collapse in the middle), but I've seen fallen cakes during my adulthood and... well... caused at least a few myself. Regarding Alice's cake falling each time one of the Brady kids stomped upstairs, I'm not sure if a series of falls could occur. IF it is possible, I think there would have to be way too much baking powder in the batter or some other inaccurate combination of ingredients that alter the chemical process during baking.
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