Castellac is referred to as a kingdom, but this is not the case. The ruler is referred to as the Duke of Castellac throughout the episode, so the area he controls would be called either a dukedom or a duchy, not a kingdom.
Two guards who are searching for Johan and Peewit used a bulldog to track their scent which leads them to a room belong to an alchemist (where Johan and Peewit secretly escaped). However, bulldogs were not used to track people's (or animal) scents during the late Middle Ages (the background of the Smurfs cartoon series), but were bred solely to bait bulls.