Katherine has two framed playbills on the wall of her apartment, one of which is the fictional "Penelope," which her character wrote and starred in. The other is the 1979 revival of "Oklahoma!," in which actress Kristin Chenoweth, born in 1968, would not have been old enough to appear.
When Katherine receives the severe weather alert on her cell phone, the word "eminent" is used when the word should be "imminent." This slight misspellings changes the meaning of the word. ("Eminent" means "prominent, famous." "Imminent" means "threatening.")
Misspelling of the word "chestnuts." The Mel Tormé/Bob Wells song is listed in the end credits as "The Christmas Song (Chesnuts Roasting on an Open Fire)."