They share an apartment at the Spinster Arms apartment complex and both work at the DMV. There have been several occasions where they've acted unprofessionally in the course of their jobs; they've given Otto Mann a driver's license due to their mutual dislike for Homer and deliberately failed Homer to show how much of a loser he was. Patty and Selma are very cynical. According to Marge, the two have very brittle necks. The two are avid, sometimes maniacal fans of the TV series, MacGyver, even getting the chance to star in their own subplot with him in "Kiss Kiss Bang Bangalore". The two seem to be aroused by the character, taking cigarettes after every viewing of the show. In "A Star Is Burns", guest-star Jay Sherman, on advice from Homer, tells them MacGyver is gay; as a result, they suspend him from the gutter. Prior to Selma's marriage with Sideshow Bob, he insulted MacGyver and the wedding was almost canceled as a result.
Patty and Selma are often shown to have gone on vacations and bringing back long dull slide shows or other activities; in "Treehouse of Horror VI", they bring a pillowcase full of seashells from their trip to Sulfur Bay for them and the family to clean and organize; in "The Wife Aquatic", they display a boring home video about Barnacle Bay; in "Kiss Kiss, Bang Bangalore", they eventually drive away Richard Dean Anderson by showing him slides of their trip to the Remington Carriage Museum in Cardston, Alberta.
Selma has actively sought out a husband, having been married a total of five times. Her current name has evolved into Selma Bouvier-Terwilliger-Hutz-McClure-Simpson and possibly -Stu, after failed marriages to Robert "Sideshow Bob" Terwilliger, Lionel Hutz, Troy McClure, Disco Stu, and Abraham Simpson. It is also implied in "Rome-old and Juli-eh" that Selma had a second failed marriage to Sideshow Bob. One person Selma refused to marry was Apu Nahasapeemapetilon, because she said her collection of last names was long enough without Nahasapeemapetilon added to it. In "Rome-old and Juli-eh", Selma began dating and later married Grandpa Simpson, who had previously dated her mother. Eventually however, they realized that they just cannot make it work because of his age and her career and called it quits. Selma has also dated Hans Moleman, Moe Szyslak, and pitifully, Barney Gumble.
Unable to find companionship in a husband, Selma has also sought to have children. At one point she was considering using a sperm donor. After babysitting Bart and Lisa for a day, she realized that although she wanted someone to love, she was not ready to have children and wound up adopting Jub-Jub. Finally, in "Goo Goo Gai Pan", a very menopausal Selma adopted a Chinese baby, Ling Bouvier. During the adoption process, Selma pretended to be married to Homer, since the Chinese government only allows children to be adopted by married couples. When the fraud was exposed, Selma managed to keep the baby, as a Chinese dignitary (voiced by Lucy Liu) who had also been raised by a single parent became sympathetic.
In "There's Something About Marrying", Patty comes out of the closet as a lesbian. Hints of her sexual orientation have been dropped many times; in "Bart After Dark" she is seen coming out of a burlesque house. She is also seen saying "There goes the last lingering thread of my heterosexuality", when Homer runs past her, naked and screaming, in "Treehouse of Horror III", and hiding in a closet with Smithers on a parade float during a gay pride parade in "Jaws Wired Shut".
After coming out, Marge is hurt that Patty had hidden her sexuality for years, but learns to respect her sister. In the episode "Homer Simpson, This is Your Wife", Patty wooed a tenured professor of Yale University away from her husband.. In "Rome-old and Julie-eh", it is shown she is attracted to Edna Krabappel. In "Kiss Kiss Bang Bangalore", Selma says "I can't face prison" and Patty replies "I can." Long before coming out, Patty had dated Principal Skinner in the season 2 episode, "Principal Charming". She refused to marry him, claiming she was too devoted to Selma as a sister to leave her alone. However, she did consider Principal Skinner a gentleman and had seemed to take it hard that she could not marry him, ending their relationship with the words "Good night, sweet principal."
Their relationship with Homer remains one of mutual dislike, which involves a continuous exchange of insults from day one, although Selma gradually grows to like Homer. They unfavorably compare their brother-in-law to a caveman, suggesting him capable of trading Maggie for beer and a nudie magazine.
Patty and Selma have occasionally expressed their common hope that Marge will eventually divorce Homer. They are often quick in pointing out how close he has come to infidelity, and have unsuccessfully offered to help Marge find a replacement for Homer, although Selma eventually gave in and helped Marge find Homer after seeing how truly unhappy she was. In the episode "Three Gays of the Condo" the twins went so far as to have a billboard built trying to convince voters to have Homer kicked out of Springfield.
Selma once took the Simpson children on a disastrous trip to the Duff Gardens theme park in the episode "Selma's Choice." She is unable to control the children, as Bart manhandles several animatronic characters and Lisa goes on a psychedelic trip after drinking "water" from an It's a Small World-like boat ride, later swimming in the Fermentarium and exclaiming "I am the lizard queen!" After that, however, Selma returned home with the children and asked Homer how he does it, referring to raising children, implying that Selma is slightly more capable of overcoming her dislike of Homer than Patty. She told Homer she just couldn't cut it today, and he comforted her. As noted above, Homer was also willing to help Selma adopt a baby, further highlighting their comparative tolerance of each other.