Adaptation Displacement: Depictions of the Last Supper almost always use Leonardo Da Vinci's painting as a reference before the sparsely detailed Biblical accounts.
Awesome Art: The Last Supper is one of the most famous pieces of art of all time for its iconic depiction of Christ and his disciples that exposes the emotional vulnerability of the Apostles through their facial expressions and hand movements.
The Last Supper is commonly referred to as a fresco, which it is not. Leonardo Da Vinci experimented with this painting, and instead of painting it on wet plaster as was the convention, he painted The Last Supper on a dry wall with an experimental mix of tempera and paint, differentiating it from ordinary frescos.
Rumors that the model for Jesus and Judas were one and the same are unfounded, as snopes.com explains in detail here.
Genius Bonus: Spotting the fact that Jesus is surrounded by a circle that implies his perfection through Aristotelian conceptions of geometry takes a someone versed in historical geometry, a field exclusively filled with geniuses and nerds.
Narm: The reactions of the Apostles are exaggerated to a point of being humorous to some. Specifically, Andrew's gesture of raising his hands is undermined by his rather blank expression.
"Seinfeld" Is Unfunny: The painting's lack of halos, realistic depiction of human emotion, and spot-on perspective will often go unnoticed by modern viewers who have seen the five centuries of art built on the back of the work of Leonardo and masters like him.
Viewer Gender Confusion: John, identified as such in the personal notes of Leonardo Da Vinci, is often mistaken for a woman due to his long hair and apparent swooning. This has even lead to wild speculation that Leonardo's John is supposed to be a depiction of Mary of Magdala, although this idea strangely leaves Jesus with an Apostle missing from his supper.
Awesome Music: A lot. Los Lobos singing "Wicked Rain", Sam Phillips' "When I Fall", and last, but certainly not least the instrumental that plays over the reveal scene.
Some Anvils Need to Be Dropped: No matter how abhorrent they might to be to you, taking someone else's life because of the beliefs they hold is an act of evil.
Values Resonance: The film's story about liberal students' increasingly extreme retribution against those they disagree—no matter how minor—became more relevant with increased political polarization that is more pronounced on internet culture of The New '10s.