Very Spooky
Characterization Marches On and Flanderization are distinct concepts. Characterization Marches On is simply when a character’s early characterization is inconsistent with their later, better-defined characterization. Flanderization is when a character’s quirk is taken and exaggerated to the point that it becomes their very personality.
back lol
There is a lot of overlap to begin with and one doesn't exclude the other. But as said the difference between them is for Characterization Marches On they possess traits that are at odds with a better defined personality (a Neat Freak was more slovenly in early episodes) while Flanderization is the exaggeration of their traits to comic absurdity (a Neat Freak becomes a massive germaphobe with their room covered in UV lights just to be careful).
Do you not know that in the service one must always choose the lesser of two weevils!
At what point should the line be drawn? On the Flanderization page there are entries about shows whose characters changed by as early as season 2, but on the other hand I see the argument that if said character used to be more nuanced in S1 it still fits the definition.