In the Batcave, Alfred can be seen polishing the giant penny to which Batman was tied during an encounter with Two-Face in Almost Got 'im (1992).
The Society of Shadows, a formidable globe-spanning organization, make their first appearance in the series. In the comics the organization was known as the League of Assassins, but the name had to be toned down for TV Broadcast Standards and Practices.
Vertigo's fall from the tower (especially the camera shot from inside the tower of him falling past an opening) appears to be a direct reference to the Alfred Hitchcock film Vertigo (1958). Another homage is the opening fall from the Statue of Freedom which resembles a climactic scene from Hitchcock's Saboteur (1942).
Helen Slater (who plays Talia) previously played Superman's cousin Kara/Supergirl in Supergirl (1984), and would go on to play Kara's adoptive mother on Earth in Supergirl (2015).