40 years after giving us the null reference, Tony Hoare declared it his "billion dollar mistake". How common are such "mistakes" in our field's history? Could we be burdened by other "billion dollar mistakes" today? It is tempting to perceive our field as one of relentless progress, with each new idea building seamlessly on the foundations of its predecessors. But perhaps our history is as imperfect as other fields: a blend of elegant solutions, practical exigencies, and costly detours, influenced by hidden corporate agendas. In this talk we sift through our history in search of more interesting, fun, and informative examples of "mistakes". Some are well-documented, like NULL and GOTO. Some are mostly forgotten curiosities like Exception Handling in the 1830s and non-binary CPUs in the 1950s. Some are the crimes of today's programming languages, arousing passionate debates like OO vs FP. Join us for a tale that will both enlighten and entertain, uncovering the lessons hidden in our past, asking which of today's practices might be considered mistakes by our successors, and offering a balanced perspective that honours the complexities and intentions behind all our "billion dollar mistakes".