These 5 shows were very popular (But how did their bad continuity impact the series?)
Stranger Things
Will's birthday is a major reference in Stranger Things as Joyce uses it as a connection to Will, directly marking the date as March 22nd. However, when March 22nd strikes again in season four, Will's birthday goes unnoticed by his friends and family. Although the episode was not written with the intent of ignoring Will's birthday, the way it is skipped over marks it as a massive continuity issue and highlights the idea that those closest to Will did not care much about his birthday.
Other big continuity issues that Stranger Things faces come from the questions of the Upside Down's origins. Stranger Things season four offers the suggestion that the Upside Down was first created when Eleven sent Vecna into the void. Nancy notices the timeline connections to her home in the present and how the Upside Down presents it, which portrays her bedroom in 1983 in comparison to season four's storyline in 1986.
Eleven's portrayal as being more verbal in season four's flashbacks than she did in season one could be written off as the events of the flashbacks being so traumatic that they resulted in Eleven's more quiet behavior, or, it could be that, in those scenes, the narrative needed her to speak more than season one initially suggested she did.
Eleven's initial quiet behavior in the first season helped play into the mystery and danger that surrounded her backstory, what these kids could potentially be really dealing with, and helps justify her strong connection to Mike, as he becomes her main tether to the world.