This chapter explores the recurring phenomena of financial manias and bubbles, as well as the difficulties mainstream economics faces in providing convincing explanations for them. While economic history is full of episodes of speculative excess—from John Law’s Mississippi scheme to the 2008 crisis—macroeconomic theory has often neglected the study of these events. Standard models, based on rational expectations and mathematical precision, are internally consistent but ignore the uncertainty, psychology, and narratives that drive market booms and crashes. By revisiting contributions from Keynes and later behavioral and narrative approaches, the chapter highlights the limitations of traditional perspectives in explaining market outcomes. It stresses the significance of Knightian uncertainty, confidence, storytelling, and herd behavior in shaping markets. Case studies of the 1920s excesses, the 2000s housing bubble, and Iceland’s financial collapse show how national narratives interact with global finance to produce systemic crises. The analysis suggests expanding macroeconomics to include uncertainty, behavioral insights, and narratives, to improve understanding of financial instability.