The act of taking a single (often minor) action or trait of a character within a work and exaggerating it more and more over time until it completely consumes the character. Most always, the trait/action becomes completely outlandish and it becomes their defining characteristic, turning them into a caricature of their former selves. Sitcoms and sitcom characters are particularly susceptible to this, as are peripheral characters in shows with long runs.

The trope is named for The Simpsons character Ned Flanders, who was originally depicted as a friendly, generous Christian neighbor and a model father, husband and citizen, making him a contrast to Homer Simpson. As seasons progressed, however, he became increasingly obsessively religious to the point where he eventually embodied almost every negative stereotype of the God-fearing, bible-thumping American Christian evangelist.