I felt the focus of the essay was on how I an interest I have can help me contribute to the classroom. I didn't have an alternate career (which I was pursuing actively outside my work). If I just had a dream of being an astronaut it will not really help me add value to the classroom, if I didn't pursue it.
What I feel is that. If you have been actively pursuing another career outside of your current work (e.g. as a part time tutor, coz u love teaching students) then talk about it briefly (what you have done about this interest of your) and then talk in detail about how this experience of yours can help you in a bschool (solve muti disciplinary problems) - like leadership, communication skills, team work, etc. If you do not have an alternate career interest that you have been pursuing actively then talk about an extra curricular activity (e.g. Soccer - that's what I talked about).
I feel it doesn't really matter what the activity is, as long as you can show how it will help you in the future. Extra points if you can even touch how it will help you with your career goals.
This is my take on this question.