In Episode 3 of Season 4 ("Open House"), Marie is wandering around a house looking at spoons. The realtor spots her and then the following conversation happens:

REALTOR: Hi. Can I answer any questions?
MARIE: Oh! Spoons...
REALTOR: Yes, the owner is quite the collector. Aren't they something? One for each of the 50 states.
MARIE: Well... Puerto Rico is technically a territory.
REALTOR: (surprised) Huh!
MARIE: You know, maybe they were thinking, "some day!".
Both laugh
I know it's an extremely minor thing, and the conversation itself is meaningless within the scope of the whole show, but can anyone explain to me what happened here?
I don't understand how a team of talented writers could produce a script with this dialogue. Nor how the actors wouldn't notice. Nor how the director wouldn't notice. And especially how the Executive Producer wouldn't have noticed during the editing.
But if it's deliberate... I still don't get it!