I have a series of programming assignments in my introductory course that has students write simple functions in Python. One of those functions is to consume nothing and returns their (the programmer's) current age. So for example, you might write

    def get_my_age():
        return 21

The students' reaction to this in office hours can be... interesting. I am curious how many of them actually follow the comment at the bottom of the question, and what they think:

> Reflect on the difference between creating a variable with a constant value and creating a function with no arguments and a constant return value.

Up to you to decide if this has any pedagogical value. The real learning objective was to "write a function that has no arguments but returns a constant value", so getting them to draw big conclusions about the nature of functions and values and so on is outside the scope of this little activity.