Langdon sees what Sophie's thinking (the she could be a descendant of Christ), and reassures her that Sauniére isn't a Merovingian name, the only ones left have the surnames of Plantard and Saint-Clair.
Langdon also feels the need to educate Sophie on all the great works of art and literature that serve as Holy Grail allegories, like Sleeping Beauty, King Arthur, and of course, The Last Supper.
Even Walt Disney was in on perpetuating the Holy Grail story. When you think about it, Cinderella, Sleeping Beauty, and Snow White are all about the "incarceration of the sacred feminine".
And don't even get Langdon started on The Little Mermaid. Phew.
Uh-oh. Teabing's back, and he's not happy that they haven't been honest with him about their little situation.