Dragon Tales is actually canon to the King of the Hill universe
Now let me tell ya
In season 6 (released 2015) Emmy and Max visited Texas with their dragon friends. They did this because they needed to buy some Propane. This was a whole arc, lasting about 13 episodes.
Great battle of Texas
In the last episode of the Propane Arc, (Room for Change) Emmy and Max had to battle the charcoal monster. This was a great endeavor, as it cause Emmy's sword to break in the battle.