What’s the coolest easter egg you noticed yourself?

I’m talking about easter eggs you noticed yourself while watching a movie, not that you learned about by reading about it. I’ll go first (it’s a long one):

I watched Kanał (1957) today and noticed something incredible. Keep in mind that it was made at a time when Poland was Communist and under a Stalinist government, so censorship was very strong. Anyway, the movie is about the Warsaw Rising, which failed because the Russians intentionally let it fail to weaken resistance for their own occupation of Poland. Obviously, Wajda (the director) could not portray this in the film because of censorship, so he hid a genius easter egg instead. In one scene where a pianist who fights with the rebels finds a piano, he is asked to play it. He begins playing Chopin’s Revolutionary Etude before being quickly told to play something else. This piece was written by Chopin in the 19th century, just after Poland had risen up against Russian occupation and been crushed. The inclusion of this piece in the film was absolutely a direct parallel to this rising caused to fail by the Russians.

This was an incredible easter egg to notice by myself. What are your similar stories?