Fixnum#times isn’t a great example, I only used it since the parent used it to illustrate their confusion and quite frankly a concrete useful example is to complex for this format.

ActiveRecord has changed a lot over the years, but as an example in the original ActiveRecord you used dynamic finders. None of the finder methods existed initially, but if you passed a message to an active record object for a non existent method rather than fail it would determine if that should be a method and then it would build and persist a method to the process for future calls.

It allows for some really interesting and powerful applications in horizontally scaling as well.