Photo credit: BBC

When Dr. Who first meets Martha Jones the building they are in is transported into space and placed on the moon.  The Doctor and Martha approach the door and the following conversation takes place.

The Doctor: Fancy going out?
Martha: Okay.
The Doctor:  We might die.
Martha: We might not.
The Doctor:  Good. Come on.

Lesson:  Taking the next step might not go so well. But then again…