Take another look at the passage:
Joey idolizes his older brother David. Combing his hair in the style that David wears, drinking coffee black with five sugars, and giving teachers the same lame excuses for late homework. As a consequence, everyone calls Joey "David" by mistake!
You chose the third part, As a consequence, everyone calls Joey "David" by mistake! This part has a main clause: everyone is the subject; calls is the verb. A fragment, however, will not have a main clause.