Do you have a stock "mock lesson" in the bag to pull out for one of those?
Sort of, but it's more like selecting from a magician's bag of tricks than dusting off a single one-size-fits-all lesson. When I have to give a mock lesson, I think about what I need to showcase to land that job (e.g. my ability to teach a subject that's called for in the ad but isn't squarely within my area of specialization, how a distinctive teaching approach I wrote about in my application materials looks in practice, etc.), and then plan a lesson that both does the necessary showcasing and includes "tried and true" material from my current or past classes.