This is due to the fact Fireys are seemingly immortal creatures that can detatch their limbs and heads with ease and reattach them at will - being playful creatures they wished to rip off Sarah's head so that she could join them in their dance, however they became antagonistic when she refused and tried to chase her down, luckily for her, she was rescued by Hoggle. Some of the Fireys appear at the party along with the rest of the creatures at the end of the film.