Maureen was an attractive person with only one visible flaw: the fact that she has a "dead tooth". As a result of her "dead tooth" Maureen suffered from severe bad breath.
After Dennis and Maureen divorced, she had a diamond stud added to her dead tooth. Later, before she was due to be married, she got her dead tooth fixed and also got breast implants.
Her father killed himself with car exhaust in his car. Maureen found his body and had to break the window of his Datsun.
Dennis dated Maureen in high school and when he was reunited with her, decided to get married. In the short time she and Dennis were married, Maureen had a craft studio (formerly Mac's room) where she would create several cat sweatshirts. ("Mac Fights Gay Marriage") The crafting and her general neediness drove him crazy and he divorced her. Maureen was apparently in massive debt (about $90,000) until she dumped it on Dennis in their divorce. ("Dennis Gets Divorced")
Maureen attended her high school reunion where she ran into her ex-husband Dennis. She showed him that she was spending his alimony payments on a diamond stud for her dead tooth. ("The High School Reunion") She watched the events of the reunion unfold, include the gang embarrassing themselves during their dance number. ("The High School Reunion, Part 2: The Gang's Revenge")
Maureen became engaged to Liam McPoyle. Their wedding was set to take place at a cabin in a remote part of the woods. Dennis was not invited, but he showed up anyway, to try to make sure that the wedding goes on, and to have both Maureen and Liam sign a legal document that would release Dennis from his financial obligations to Maureen.
When Dennis saw Maureen, he immediately noticed that she has gotten breast implants and gotten her "dead tooth" fixed, which made her far more attractive to Dennis. When Dennis asked her why she didn't do that when they were married, Maureen responded that she was willing to change for him, but he never asked her to. Maureen's bridesmaids run Dennis off before he could get her to sign the document. After the wedding has descended into chaos (and quite possibly a zombie infestation), Dennis found Maureen again. She was crying so he comforted her, eventually banging her. He thought it terrible, though — he told her that her nipple placement was terrible. Worse for him, Maureen seemed to be completely in love with him again and refused to sign the document, saying they should run away together. ("The Maureen Ponderosa Wedding Massacre")
Maureen has had a series of plastic surgeries to make herself look more like a cat (because "Cats are magical", of course), including moving the breast implants that had impressed Dennis so much earlier into her face, and affecting cat-like mannerisms, like saying "Meow-yes" when she's asked a question. ("Mac Kills His Dad")
Maureen has now accepted her feline emotions and begun her transition into a cat, during episode 7, she will now only be identified as a cat, rather than a human, much to Dennis' despair (as he still has to pay her alimony). Answering in a series of 'meows', hissing when she is threatened, and chasing a laser pointer through a Court of Law, Maureen and those she surrounds herself with must now succumb to her cat-like instincts. ("McPoyle vs. Ponderosa: The Trial of the Century")
Maureen continues her transition to being a cat, changing her name to "Bastet", after the Egyptian goddess of cats. According to her brother, she also started using a litter box. She was scheduled to have a "reverse nipplectomy" to add more nipples to more closely resemble a cat, which Dennis would be obligated to pay for. Bastet/Maureen is later found dead from a broken neck, and Dennis is the prime suspect. It eventually turns out that she died of an accidental fall trying to climb over the roof of a building, and Dennis is cleared. ("Making Dennis Reynolds a Murderer") Not many people missed Maureen, with her own brother, Bill, believing that she died three years ago upon her transition to being a cat. In fact, to some, Maureen's death was blessing in disguise, as Dennis, after three years, no longer had to pay alimony to his hated ex-wife, with Bill even stating that even if Dennis did in fact kill her, "he did them all a favour".
- Season Six: "Mac Fights Gay Marriage," "Dennis Gets Divorced"
- Season Seven: "The High School Reunion," "The High School Reunion, Part 2: The Gang's Revenge"
- Season Eight: "Maureen Ponderosa's Wedding Massacre"
- Season Nine: "The Gang Saves the Day" (in a flashback sequence)
- Season Ten: "Mac Kills His Dad"
- Season Eleven: "McPoyle vs. Ponderosa: The Trial of the Century"
- Season Twelve: "Making Dennis Reynolds a Murderer" (Photos only)
- It’s Always Sunny: Gang Goes Mobile
- Maureen: (referring to her father) Suicide. Car exhaust. I had to break the window of the Datsun. His eyes were so yellow.
- Season Six, Mac Fights Gay Marriage
- Maureen: (to Dennis) Now you get yourself on that couch, I'm going to make some fish sticks.
- Season Six, Mac Fights Gay Marriage
- She has a brother Bill who dated Dee.
- Maureen is very into cats. She enjoys eating fish sticks and wearing sweatshirts with pictures of cats on them.
- In Season Seven's "The High School Reunion," Maureen bought a diamond stud for her dead tooth.
- In Season Eight's "The Maureen Ponderosa Wedding Massacre", Maureen got her dead tooth fixed. Also, she had a plastic surgery to get herself some "big giant new titties". Dennis states that the boob job was done horribly.
- In Season Ten's "Mac Kills His Dad" Maureen begins plastic surgery to transform herself into a cat-person.