Need a quick math-and-science thinking activity that is easy to access and ready when your lesson plan suddenly changes? This Mystery Doug YouTube video lesson turns the short clip “What’s the Biggest Number?” into a focused, no-prep worksheet students can complete before, during, and after viewing. This resource is built for the reality of a busy classroom: a 5-10 minute YouTube clip, a clear student worksheet, a teacher answer key, Google Classroom options, and a 10-question self-graded quiz.