Abby is the niece of Glenn Quagmire and daughter of Brenda Quagmire. She suffers from brain cancer.
In "Screams of Silence: Story of Brenda Q.", Brenda reveals to be pregnant with her and her then abusive boyfriend Jeffery Fecalman. Which would end up being Abby.
In "Road to the North Pole", her uncle takes her to sit on Santa Claus's lap at the mall so she can tell him what she wants for Christmas. Her uncle's enemy, Brian Griffin, tries to make amends with Uncle Glenn by being nice to her. However, he mistakes her for a nephew and scares her into thinking she's dying.
When Brian and Stewie get home, Lois gets a call from Glenn saying that Abby's cancer has returned and that she is in the Intensive Care unit at the hospital.
In "The Quagmire Show",
Abby is voiced by Karley Scott Collins.