Goof: The mayor said that the Eunice duck was sleepwalking, but it is clearly seen that she woke up before running away.
Goof: They never mentioned again or explained what the "Once Upon a Time" sign was doing on the road, or who put it up.
The person who was transformed into a duck wasn't really a prince. He was a farmer, but his name was Jeremiah Prince.
Eunice being put to sleep:
The plot twist about the mayor's daughter being put to sleep by an evil hermit and that she could only be awaken by the kiss of a prince, is an allusion to the fairy tale "Sleeping Beauty".