Mary McGuffin was a line of dolls that were probably very rare and hard to get. The Mary McGuffin line of dolls has been discontinued, possibly because many people get into fights to own one, like how Candace and Vanessa did. (Finding Mary McGuffin) The Mary McGuffin dolls were made of plastic. (Not So Bad A Dad After All) The name of the doll refers to a MacGuffin, a common item in TV shows whose single, sole purpose is to drive the plot of the episode forward, either directly or indirectly.
Candace's doll[]
Candace's Mary McGuffin doll
Candace had a Mary McGuffin doll with light brown hair and wearing a green dress. She probably liked the doll a lot, as when she found out that her father had sold the doll for one dollar at a garage sale, she was very upset and went around town looking for it.
The Mary McGuffin doll was bought by Doofenshmirtz for his daughter, Vanessa, who had asked for a Mary McGuffin doll 9 years ago, when she was 7. Since then, although Doofenshmirtz had a hard time looking for it, he never stopped.
When Vanessa received the doll, she appreciated it very much, but soon after, it accidentally got donated to one of the many Charitable Charities in Danville. When it was found on top of a shelf, Candace and Vanessa fought for it, and it ended up in the hands of a little girl who now wanted the doll as well. Candace gives up hope and says that she is too old for dolls anyway, while Vanessa snatches it from the little girl, making Heinz think she's becoming evil. The doll currently belongs to Vanessa.