 The scene in which Buffy, Xander, Willow, and Giles stand and  discuss what theyll do the next day, which ends with Giles saying  to himself "The Earth is definitely doomed" is an homage to the very  first storyline of the series which takes place over the first two  episodes of season 1. Ep. 1.02 "The Harvest" ends with Buffy,  Xander, and Willow walking away talking about ways for Buffy to get  herself kicked out of school, and Giles turns and mutters "The Earth  is doomed".