As the players travel along the trail, they notice a bear in the woods, following thier moves. It does not make any agressive moves, but neither does it leave. As daylight fades, the players need to decide what to do. Is it a spirit guide, or gaurdian to the forest; is it a lycanthrope, or being controlled by evil spirits; or is it just a curious bear?
Magic should have side effects, both expected and unexpected - fortuitous and deplorable. Expected side effects add anticipation, while unexpected ones increase the drama of the scene. The result can be comedic or dire, it dpends on which circumstances work best for your game.