This is the Barbie hairstyle I named "Yet Another Musketeer" (number 10) in this Barbie Hairstyle post. It isn't exactly the same, but close enough for me. This special guest is my neighbor friend. She asked me for help to do her hair for a dance competition. She said that it lasted for her second day of dancing, and she just needed to spray some flyaways after she slept on it.
Start with a ponytail. Next you'll need to use a sock to form the bump. Cut the toe off a sock and then roll it until it looks like a doughnut. Put the tail of the ponytail through the hole. Spread the hair over it evenly, and then add another hairband.
Tuck the little tail in under the bun, or if you can use it the next step. Now you will need to do a french hawser twist around the bun. Take up two sections of hair from beside the bun. I did it on the side, but taking it from the top may make it less visible where you start from. Twist each section one direction, then wrap them together in the opposite direction. Add more hair to the sections as you continue twisting around the bun. When you run out of hair to add in, keep twisting the ends together and put a clear hairband in the end. Wrap it around the bun and tuck the ends underneath to hide them. Use bobby pins to hold it all in place.