Wikisimpsons - The Simpsons Wiki
The twins are quite bright students (they even have their own language) and are often very conniving and mean, even to each other. When it comes to Bart they are quite stuck up, and never miss an opportunity to berate him. They fed Bart intentionally false information on American history, however both girls correctly guessed that Bart had not prepared himself for a test and was looking to get all the answers from a student who studied, so the prank was arguably to teach Bart a lesson in slacking; since if he had studied he would have realized the information was incongruent. Bart appears to have a crush on one of them. Sherri referred to Bart as an ugly, smelly dork, but was convinced by Homer to go on a date with Bart after he told her that neither she nor Bart could do much better. One of the twins stated that her sister had a crush on Bart it is unknown if this is the truth or if it is just teasing  She also has a "boy crazy" cousin who has a crush on Bart.
When it comes to Lisa they are just as inconsistent. One minute they will be friends on the schoolyard playing together and the next they will be ganging up on her. More often than not it is the latter, usually not including Lisa because she is too smart or too weird. Once they said her butt was too fat causing Lisa to go on a diet.
Professor Frink shows Bart and Lisa a possible future with his astrology machine. It is revealed that Nelson Muntz simultaneously dated and impregnated both Sherri and her sister, who bore him four children (two sets of twins, naturally) shortly before Nelson's high school graduation. He abandoned them during Bart's graduation party, using the same statement his father said to him before abandoning him.
 The Simpsons arcade game
Sherri appears in stage 1 and 2 carrying a plate of food for the Simpsons to gain health.
 The Simpsons Game
Sherri and Terri appear as one of the holders of the three Sparklemon that Homer and Lisa must defeat.
 Behind the Laughter
They have similarities to The Grady Twins (ghost girls) Danny sees in Stanley Kubrick's adaptation The Shining, of Stephen King's novel of the same name. In a deleted scene of the parody of the Shining called "Treehouse of Horror V" they are ghost twins seen by Bart. They also take on this role in The Simpsons Game; they are in a game engine elevator saying "Come play with us, Simpsons".