Factual error: The forces of Cassiopeia all sport the crown-like "W" sign which is the shape of that constellation... but only as seen from earth! These five points in three-dimensional space (like all star signs named after anything) look like that when viewed from our own planet; but from anywhere else, they aren't shaped like that at all. Why would they chose to see themselves through a very specific angle of view from some other distant planet (earth)?
Continuity mistake: When the teacher is asking the class questions about the declaration of independence, she has some info about it written on the blackboard ending with "1776 in." Then facing away from the blackboard, she asks a question and Mr. T quickly answers and then only a second later, the camera is back on the teacher and suddenly the world "PHILADELPHIA" is on the blackboard under the "1776 in" with no time for her to have written that word in one second.