Prior knowledge has been a key construct for theories of memory, comprehension, and learning. And traditionally prior knowledge has been identified as a resilient source of information, standing strong in the face of even the most compelling refutations and evidence. In the current talk I describe experiments that call into question this characterization of prior knowledge. Work from my lab shows that well-worn expectations appear malleable (and sometimes even non-existent) when people are confronted with contradictory arguments and facts. Across a variety of demonstrations involving the presentation of text content containing potential misinformation, people subsequently rely on encoded inaccuracies leading to problematic and surprising demonstrations of ignorance. Even obvious misinformation, which individuals should know better than to fall for, can influence subsequent problem solving and decision making behaviors. This talk will identify the consequences of exposure to misinformation, as well as highlight important boundary conditions for when and how people might be encouraged to engage in more critical evaluation in the service of successful comprehension.