In the Simpsons S28E3, titled The Town, Simpsons try to permanently move to Boston. Lisa gets really fond of Boston, as most of the town is made for intellectuals like her. Eventually the get back to Springfield, leaving Lisa frustrated by the decision. Marge makes a promise that someday they will get back to Boston, to which Lisa answers that she has never left it. She starts to hallucinate about Boston and her eyes turn into a red triangle (screen capture below).
So what does the red triangle shaped eyes mean? How's it connected to Boston?