Martha is probably best understood for attempting to sell Martin's extremely valuable Star Wars merchandise to Comic Book Guy for an extremely cheap price. She was warned by Bart and Milhouse before she sold them and she chose to not to sell it. In Wild Barts Can't Be Broken, it is revealed by her son that she "shoplifts all the time, mostly just for stuff she doesn't even need."
She was also responsible for all of the guests at Martin's birthday party (with the exception of Seymour Skinner, Edna Krabappel and Bart and Lisa Simpson) getting food poisoning because she had served diseased oysters instead of cake.
- Seymour and Edna didn't get sick because they were in Martin's pink playhouse and therefore didn't receive any oysters.
- Bart didn't get sick because he fed his serving of oysters to the Prince family's pet cat (who got sick from eating them).
- Lisa, being a vegetarian, didn't actually eat any of the oysters--as she explained to her brother, she simply wanted an excuse to leave the party without seeming rude.
- It is possible that Mrs. Prince may have kleptomania, due to Martin's comment about her shoplifting habits.
Note: Many of her appearances are brief background roles. The episode in which she has an actual role is in bold.