Rewigging

Rewigging is the fandom term for taking the wig off of a doll and replacing it with a different wig. Because AG dolls have glued on wigs and the heads are bald underneath, wigs are easily swapped between dolls.

Reasons for Rewigging
The most popular reason for rewigging a doll is to create a new or unique character. With a different wig, a doll can look quite different from her original AG look. AG only has certain combinations avaliable, and those who seek to try other combinations may swap wigs or use brand new wigs to get new looks.

Another pupular reason is wig damage. People who purchase secondhand or used dolls quite often purchase dolls who have haircuts, hair damage, or tangled hair that cannot be managed or corrected easily and a new wig starts the doll fresh.

Somtimes there is the desire to preserve a face shape or mold. When a doll is sent to the american Girl Doll Hospital for hair damage, the doll is simply given a completely new head. For people who have PM dolls with hair damage, they many times wish to keep this head rather than have it exchanged for a Mattel head and will rewig the doll themselves.

Another reason is to simulate limited edition dolls--since Kailey and Lindsey are hard to find on the secondary market, some people will simulate the dolls by using a like wig on dolls that resemble them. This is generally acceptable when done to a doll that is then kept in a personal collection; however, selling a doll this way without specifically identifying that it has been "frankendolled" is greatly frowned upon.

Wig Size
In standard doll wig sizing, an AG doll wears about a 10 size wig.

How to Rewig
If the doll has a wig on, this wig must be removed. If the wig is badly damaged, it is not necessary to preserve this; if the wig is to be kept, it should removed slowly to preserve it. Once the doll is ball, the new wig may be placed on the bald head. Many people choose to glue the wig down with a firm adhesive; others who plan to change wigs frequently leave the wig loosely attached so that it can be easily swapped.

A comprehensive guide on rewigging can be seen here: http://www.justmagicdolls.com/articles/rewig/rewig.htm