Nancy

Nancy is the biological mother of Jeffy. She was a mentioned character in Mario The Babysitter! and Jeffy's Sister! and finally debuts in Jeffy's Parents! as the main antagonist. She is an alcoholic and abusive prostitute who abandoned her son with Mario because she hated him for obvious and unknown reasons.

One year later, during the events of Jeffy's Parents!, Nancy comes to Mario's house to get Jeffy back after finding out that Jeffy was to inherit millions of dollars from his father, Jacques Pierre François, who had committed suicide for the sake of his artwork. Even though she beat up Jeffy and belittles him in front of Mario and Rosalina, Mario didn't care, while Rosalina is concerned. In the car, she starts beating Jeffy senseless, until he escapes and goes back to Mario's house, begging Mario to let him stay with him and the gang. He also genuinely promises to stop annoying Mario and disobeying him (which he eventually breaks). Then, Mario calls the police on her, and she gets arrested for child abuse, prostitution, and "a bunch of other things". Mario then decides to adopt Jeffy and let him stay, as long as he behaves. But Mario probably let him stay because he secretly loves Jeffy.

Trivia

 * While it's said that Nancy and Jacques Pierre François hated Jeffy, the note may actually mean that they care about their son and Jeffy may have been kidnapped. This probably wouldn't have happened if they hated Jeffy, however, it's revealed that Jeffy's mom didn't care, so it's possible that Jeffy's Dad was the only one who cared.
 * When Brooklyn T. Guy states that Nancy is arrested for "a bunch of other things", it is assumed that Nancy is charged with: Motor Vehicle Theft, Prostitution, Child Abuse, Child Neglect, And Child Abandonment. Her prison sentence is unknown, but due to Florida's laws about M.V.T, it'll be at least 10 years or so.

Reception
Throughout Jeffy's Parents, Jeffy had flashbacks showing how abusive she was to him. Thus, begins the fandom to believe she is unkind, insincere, and a liar for displaying acts of "affection" to him around Mario and Rosalina. When Nancy abused Jeffy (like restricting him for eating for a week), this left most of the audience in anger and disgust towards her. The small minority of people who had a deep disliking for Jeffy were glad she abused him, and then gave a reason as to why he "tortures" Mario.

But, the large majority of the audience have a deep disliking towards her and she was heavily panned by the large majority of the audience, and she is one of the most hated characters in the series. Unlike Jeffy, however, who most fans also hate, Nancy was specifically written to be unlikable.

Poll
Do You Like Nancy? Yes! No! Kind Of.