Beckett's mother's tombstone reads "vincit omnia veritas" which is Latin for "truth wins everything" (literally) or "truth conquers all". It is, however, written somewhat unusually, as typical Latin practice is to put the verb at the end of the sentence, thus: "omnia veritas vincit".
This is the highest rated episode of the series
The high school name that is on the podium is Marlowe, a nod to the series creator.
In a deleted scene, Castle mentions that he is planning on resurrecting Derrick Storm. Though excised from the final episode, this was likely meant to be a reference to Arthur Conan Doyle reviving Sherlock Holmes, by popular demand, after killing him off in the short story "The Final Problem".
According to Johanna Beckett's grave, she was born February 4, 1951 and died January 9, 1999.