Constitution Day is a celebration of the US Constitution, observed on September 17, the day in 1787 that delegates to the Constitutional Convention signed the document in Philadelphia. More details here.
In this clip from Star Trek (Omega Glory episode), the Constitution is rediscovered (in a parallel existence) after a long period of misinterpretation, and only Kirk knows its importance…not that such a thing could ever happen. Ahem.
This classic Bugs Bunny/ Daffy Duck cartoon explains the Constitution’s separation of powers and the Bill of Rights, as a conniving Daffy Duck is frustrated by these features when he tries to use government power to outlaw Bugs Bunny.