Jacob Stone's car lot of "perfectly average cars" are all Studebaker Lark variants.
Declaring "We're the Librarians" to get past officials finally works for the "junior" Librarians, where previously only Flynn was able to pull it off.
The plot of the series' finale is a perfect bookend to Judson's advice to Flynn in the first Librarian movie: "Trust no one".
Regarding the 'permanent treatment', an orderly says, "They don't drill holes in your skull anymore; they do it through the eye socket instead". The first lobotomy, performed in 1935, involved drilling holes in the skull to access the brain. In 1946 the pre-frontal lobotomy was developed and involved shoving an ice pick through the top of the eye socket which is also the bottom of the brain pan, then swishing the pick back and forth to destroy the frontal lobes. A pre-frontal lobotomy can be performed in 30 seconds with just an ice pick and a mallet and leaves no visible wounds beyond slightly blackened eyes.