At about 23 minutes in, Parker is wearing the same flight attendant outfit she stole and wore in S1E8 The Mile High Job.
When Sophie shows Nate the storage unit containing all of the items she's stolen, the chalice she picks up is the prop used as the Judas Chalice in The Librarian III: The Curse of the Judas Chalice (2008), which was also produced by Dean Devlin.
The rooftop scenes were filmed in Pasadena, California. The city hall dome and San Gabriel Mountains are clearly visible in the background.
Christian Kane and Clayne Crawford previously starred in The Donner Party and are very good personal friends.
In 'Christian Kane's show The Librarians (2014) he is the world's top "5" art experts. The reason it is 5 is because he uses aliases to show his expertise to the outside world, as well as when he publishes articles. He never used his own real name until the end of season 2.