Darla:

Back in the day Darla had a lot of different styles...
In the beginning of BtVS Darla had a weird bob style that made that catholic school girl outfit even more scarier.
After her resurrection her hair was longer with a few nice curls.
Darla's hair was a lot sleeker in the middle of season 2.
Darla's hair got shorter...
What better way to ware you hair for a massacre?
In season 3 her hair was longer and messier...