My character needed to make a 3 hour flight across the country to help a comrade in danger. Ideally, he needed to be there in minutes.
The Bureaucracy of the organization he worked for was preventing him from acquiring a plane, much less trying to fly it there quickly. I declared that an NPC we had previously helped 'just happened' to arrive on the scene. The NPC was an expert world-walker.
Coincidentally, the NPC I 'declared' was the same PC that Sanctaphrax just mentioned (I think)