Corrected entry: Most of the gadgets Kim uses just couldn't work, simply for space reasons. For instance, the hair drier/ grappling hook couldn't work, because the hook is much larger than the opening it comes through. Also, all that rope couldn't fit inside that hair drier. The Kimmunicator has so many attachments that they couldn't possibly all fit inside it. In "A Stitch in Time Part One: Present" When Kim is going land surfing in Australia, the keychain-sized land surfers expand into regular sized land surfers, which just isn't possible. Mistakes like these run throughout the series.
Corrected entry: In A Sitch in Time, we see that it takes Ron all night to get half way around the world to help Kim. However, Kim seems to be able to impossibly get half way around the world within an hour almost every episode.
Correction: The scenes don't prove that it takes Kim less than 1hour because it cuts to the end of her trip which could be 24hours or more later.
Correction: Which makes sense, seeing as how the show doesn't "fit" into reality. How many teen superheros do you know?