This is a common question to try and ascertain a bit more about you and your personality.
It is fine to be quirky if your outside activities are a bit quirky!
However, if your outside interests could be considered controversial- step a little lightly.
For example, if you go on anti-hunting protests that is great, but your employer may be concerned that you could get arrested and also it is possible that they are pro-hunting.
In this question, it is also worth communicating what you consider to be stressful.
One candidate may find a messy desk stressful, whereas another candidate may consider human conflict more stress inducing.
Neither one is necessarily better or worse, but your prospective employer will be trying to assess your stress levels- but more importantly how you manage that stress.
Be prepared to ask your prospective employer questions.
This is important- it shows that you are taking working for them as a serious proposition.
The questions can range from practical things like “when I am likely to hear from you or when would I be expected to start” to questions about the organisation