Gibbs wears a small patch on his combat vest that reads 'NKA'. This simply indicates that he has No Known Allergies.
The English nanny that Vance is interviewing carries an umbrella like Mary Poppins and is named Maria, like the heroine of "The Sound of Music". Both were played by Julie Andrews.
When Tony and McGee are chased by the dogs from "Pitt"'s house, Tony yells "Zeus, Apollo! Stop" This is a reference to the two Dobermans from the 1980s TV show Magnum, P.I. (1980), in which Robin Masters' dogs Zeus and Apollo often chase people off the property. Donald P. Bellisario created Magnum PI and NCIS.