Casting Patrick Cassidy as a second generation villain is a homage to his father Jack Cassidy playing the archfoe Max Mencken in the 1966 Broadway musical It's A Bird, It's A Plane, It's Superman! -- a role Patrick himself played in a 2010 revival. Patrick Cassidy also went on to play Lana Lang's biological father on Smallville.
Mr. Smith: I don't care what anybody says - nobody wrote an opera like Puccini.
Vixen: I want to kill Superman.
Mr. Smith: Not an opera-lover, I see.
Vixen: I am Vixen. I eradicate evil, just like you.
When "Mr Smith" is speaking to his henchmen about killing Leslie they pan around the back of the head of the bald guy and the tattoo that he has on his neck is "Tanaka" in Kanji. This is the same tattoo that Dean Cain has on his left ankle.
This episode, with the next two ones, can be also called "The Lex Files" arc.
When the camera pans across "Mr Smith's" underground lair you can see Starro, the evil alien starfish who invaded Earth in the early Justice League of America comics, in the graffiti on a support beam.
In one scene, "Mr. Smith" is listening with unabashed rapture to an operatic aria - the music is "Un Bel Di" from Giacomo Puccini's "Madama Butterfly."