A very loud overbearing woman, she was largely responsible for Frank's nature. Peggy often neglected her son and treated him very coldly, this would be reflected in her son's own parenting to his children. Peggy later emasculated her grown son and was notable for being the only person to shut him down completely.
It is from Peggy that Frank developed his manipulative nature, this was seen when Peggy bribed her grandchildren with gifts and money to get on their good side and turn them against Frank until she was exposed. Like her family, she has violent tendencies but Peggy is much worse, as she once shot at Sheila, made plans to kidnap the children of her old drug buddy, and stabbed her own son in the leg with a screwdriver for trying to swindle her.
In spite of her vile nature, she does come through for her family as she was happy when she met Lip and Ian. She spent time with the youngest grandchildren, though she was a bad influence on them. While it is unknown how she treated her other sons, she admitted to being a terrible mother and seemed to care about them as she called Wyatt her baby and sent all her money to them as she was proud for how they turned out. Though Peggy treated Frank with disdain, it was interesting to note that she chose to stay with him than her other sons. Peggy even expressed pride in him for ripping off the state by pretending to be Ginger.
She is first mentioned in Nana Gallagher Had an Affair, where after the Gallagher kids inform Frank that he is Liam's biological father. He mentions the rumor of his mother sleeping with a black man, realizing the affair is what conceived him to make his parentage possible.
She physically appears in Daddyz Girl, where Peggy was visited in prison by Lip and Ian. She was unaware of who the boys were until they inform her that they are her grandsons, via her son Frank and she gets pleased by this news after remembering them and they catch up. Peggy notices they must want something for them to visit. The three talk with them asking about her other sons, since they learned one of them might be Ian's true biological father. Peggy was not too surprised by their mother having an affair, though she gives them the names after she has them promise to get her cigarettes. Before leaving, she has them to tell her son Jerry that he still owes her money or she'll send her ex-husband Ronnie to his home and hurt him.
In Can I Have a Mother, Peggy is sent home from prison after supposedly lying about her health. She immediately makes herself at home in the Gallagher Household, where she meets her other grandchildren Debbie, Carl, and Liam with them being surprised to finally see her. Peggy then knocks out a piece of the wall, she claims a gun and money while telling the kids not to tell Fiona as they are more than happy to keep her secrets after being handed a $100 bribe. Peggy later has Carl take her to the Alibi and she finds her son Frank, who is horrified to see her released. Peggy then shanghaied her son into helping her go after an old dealer who profited from her arrest. Peggy soon makes an enemy of Sheila, with her rude nature. On the drive, Frank attempts to reconcile with her by telling her about his kids and praising them but she isn't interested. She later confronts the dealer Noah Pitts who is now a surgeon and demands money from him, though he couldn't pay and she planned to kidnap his daughters. Frank steps in and ends up ruining the deal by warning the man and only getting a quarter of the promised 200,000 dollars. The mother and son are shown to have a frosty relationship, as she stabs him in the leg for trying to swindle from her. She attends a party at the Jackson house, where she is still rude to Shelia who she even tries to shoot but is stopped by her family. Afterwards, Peggy gives Carl and Debbie gifts for their recent help of her and they are more than pleased by this. Soon, she talks with Fiona and gives her money to fix things up, while offering more time to learn about each other since they missed out. When Frank goes through the mail, Peggy reveals that she has the letter that he's searching for and praises Frank for lying to the state about the dead Ginger to get benefits. She decides to make herself at home and take his room. However, Frank tells her off and states that he won't subject to her will, before ordering her out. She is unfazed and gets him to comply by insulting him and coldly labeling him a loser. Fiona overheard the argument between Frank and Peggy and now sees why her father is the way he is since he had a horrible parent just like her. Fiona comforts the sulking Frank and he accepts it.
As of A Bottle of Jean Nate, Peggy still has Frank tend to her and ignores attempts to reconcile with him. In spite her hostile nature, she tries her best to reach out to her grandchildren, giving Fiona money and showering Carl and Debbie with gifts. However, she was also trying to manipulate them to gain their trust and this nearly works as Fiona liked having her around and ignored Frank's pleas. Peggy also embarrasses Frank in front of the Alibi patrons. At home, she has Lip and Ian settle their issues by fighting as she had her sons do as teenagers. Fiona realized the truth of her grandmother after she saw Peggy was trying to run a meth lab in the basement with Carl who was nearly caught in an explosion. Fiona and Frank plot to get rid of her only to discover that she really is dying of terminal cancer and doesn't have long to live.
During Parenthood, she eventually gets sick to the point where she is unable to do much and Frank now having the upper-hand against her abandons his servant role to her. Peggy makes amends with Sheila and tells her that she has acknowledged how she is a terrible mother and sends out money to Frank's brothers instead of Frank himself since she wanted to spite him for taking her morphine. Peggy later shows that she wants to hasten her death, such as to get hit by a bus to sue the city, only it failed after Jody stops her. She soon gives Sheila permission to kill her, but not before In the end, she is suffocated with a pillow by Shelia at Peggy's request. Frank soon walks in on Sheila smothering her, he is confused by what's occurring and Sheila tells him that Peggy died. Frank (putting things together) rejoices at finally being free of his mother's influence. However, he is later angered to hear that she sent all of his brothers money while leaving him nothing.
In Just Like the Pilgrims Intended, the Gallagher children are informed of her death and break down at this, despite the trouble they went through with her. Frank later meets his brother Clayton and mentions to taking care of their dying mother without help from him or their brothers. Clayton justified that he had no idea Peggy was even released and he has spent the money that she sent him on his mortgage, to Frank's displeasure. After her death she is cremated, and Frank doesn't want anything to do with his mother's remains. Her ashes were brought back home by Monica the morning after Peggy's mourning. During this time Mandy was pregnant, which made Terry very upset. Frank began to prepare a smoke made from his mother's ashes, Terry breaks in the back door looking for Ian and knocks the bag of ashes from the table and on to the floor.
In Order Room Service, Frank bonds with Carl and talks to him about his siblings turning on him. Frank mentions that he never did that to his mother while listing all the terrible things she did and the abuse he suffered before cursing her name.
During A Jailbird, Invalid, Martyr, Cutter, Retard, And Parasitic Twin, Frank tells his oldest daughter Samantha about Peggy having an affair. He mentions his father beat him for not stopping his mother and how she got off scott-free for the acts. Sammi was surprised at this and criticized how this went on.
In Emily, Frank mistakes Sheila for his mother while in delirium but disturbs her with suggestive tones.
In Los Diablos, Frank mentions to Mikey O'shea on why he should be the ideal person for hobo loco by mentioning Peggy stating he buried "a mother who never loved him".
- Can I Have a Mother
- A Bottle of Jean Nate
- Parenthood (Death)
- Just Like the Pilgrims Intended (mentioned only)
- Order Room Service (mentioned only)
- A Jailbird, Invalid, Martyr, Cutter, Retard, And Parasitic Twin (mentioned only)
- Emily (mentioned only)
- Los Diablos (mentioned only)
- Similar to Monica, she had a terrible effect on Frank and caused most of his insecurities and terrible habits to emerge.
- According to her, she slept with some of the female inmates of the prison.
- She most likely went to jail before Debbie, Carl, and Liam were born since they didn't know her.
- This was supported by Fiona being eleven when she was locked up.
- She was familiar with Kev and Veronica.
- She did twelve years out of her 20 year to life sentence.
- She may not have been on good terms with her other sons either, as her son Jerry Gallagher owed her five grand and seemed to know his nephews were sent by her while Clayton Gallagher was unaware she was released from prison.
- Despite that, while dying she sent all but Frank money.
- Apparently, she had a rumored affair with a black musician and the result was Frank and Jerry.
- This means that they are biracial and the traits skipped a generation and passed onto Frank's son Liam.
- Season 10 retconned this with Monica's family having an affair.
- She never liked Monica for being with her son.
- Coincidentally, Monica's father didn't like her son for being with his daughter.
- She never met her oldest granddaughter Samantha.
- It is also unknown if she was aware of her as Frank was. However, Samantha learned about her when talking to Frank.
- She never met her great-grandchildren Chuckie, Franny, Freddie, and Carl's unnamed kids .
- It is unknown if Ginger Gallagher was her sister or sister-in-law.
- It is unknown if Patrick Gallagher is her nephew or of Frank's father from an unknown sibling or a distant relation.