During the obstacle course scene, when both Greg and Marcia are driving, sometimes you can see a white car (possibly a Volkswagen Squareback) in the distance behind the family, and other times it is not there.
Marcia's temporary license says it was issued on January 15, 1974, which is four days after it was originally aired.
When Mrs. Brady and Alice are cooking, the stove is clearly not on. It is a gas stove and there are no visible flames (this happens in multiple episodes).
As Jan is talking to Marcia in the bedroom, they are both facing the mirror. A shadow from a boom mic can be seen to the left of the mirror.