A Frankendoll is a doll noticeably put together or created from other doll parts. The word is a portmanteau of "Frankenstein" and "doll".
Technically, any doll that is customized or modified with American Girl doll parts could be called a Frankendoll; however, this is generally applied to dolls that are meant to deceive other collectors and/or purchasers. The most notorious application of frankendolling is taking a modern doll and rewigging her to resemble a limited edition doll.
For example, JLY 23, who has freckles, can be rewigged with a short dark brown curly wig to resemble Lindsey. This has also been done with Kailey and brown eyed dolls. There have yet to be a report of a rewigged JLY 28 passed off as Marisol or a JLY 30 passed off as Jess; however, those dolls have been fairly plentiful for secondhand purchasing and do not command the same high secondhand prices.
Other types of frankendolls include dolls who have been assembled from spare AG Hospital parts and sold at the American Girl Benefit Sale. The specific vinyl tone on the head of the doll and her limbs may vary in this type of doll; an example is a Pre-Mattel JLY 4 with the golden skin tone on her head but with a Caucasian body. Such dolls can also be created from pieces of broken dolls by collectors and restorers.