retarted?
Obviously he is employing the older use of the word, "tart," noun, a woman considered to be sexually promiscuous or a prostitute. These woman were at one point, tarts, but had become normal since coming to the United States of America at some point. Upon their return to Canada, they "retarted" themselves, leading to their awkward appearances and odd demeanor. I say a return to Canada, because in the 15 seconds I watched of the video they did not pull the "duck face" once. This duck face has become a staple of American tart culture and its lack of appearance is a red flag. More specifically, a flag consisting of a red field with a white square at its center, in the middle of which is a red maple leaf.
Canada.
All the win of the world.