Mr. Freeze is kidnapped from Arkham by Grant Walker, an aging billionaire who desires to become immortal by going through the same process that Victor underwent (as it slowed his metabolism and cryonically preserved his cells). He convinces Freeze to help him in exchange for curing Nora. It becomes apparent when Batman and Robin arrive in Walker's private city off Gotham's coast, Oceana, that he has more than just his own immortality in mind. Namely that he plans to freeze the entire world so that his chosen few can live on in his personal utopia.
- Affably Evil: Grant Walker is very warm and welcoming... for a guy who wants to kill the world to create his own utopia.
- Always Save the Girl: Grant Walker wants to use his technology to freeze the planet, killing everyone except those on his island. In exchange for his cooperation, Walker offers to revive Freeze's wife. Freeze is willing to go along with the plan until Batman points out that Nora would be waking up to a cold, dead world and would hate Freeze for helping to cause it. Freeze then releases Batman and Robin and helps them defeat Walker.
- And I Must Scream: In addition to building a "perfect" society on an island of his creation, Grant Walker convinces Mr. Freeze to give him the same mutations as Freeze himself, allowing him to live forever. However, after Batman convinces Freeze to stop Walker from freezing the rest of the world, Walker ends up trapped in a block of ice, lost at sea, COMPLETELY AWARE OF EVERYTHING AROUND HIM, YET UNABLE TO FREE HIMSELF OR EVEN MOVE FOR THE REST OF HIS IMMORTAL LIFE. As is to be expected, the last we ever see or hear of him is his anguished scream of horror, a scream that no one else can hear.
- Well, he was. A comic followed up his story by showing that he managed to get out (cause icebergs do melt ya know?) and tried returning to Gotham to get revenge upon Freeze after finding out that Freeze's condition had destroyed most of his body and the same thing would happen to him eventually. He was captured and imprisoned after Freeze almost killed him.
- Artistic License Chemistry: Grant Walker is encased in a chunk ice, which sinks to the bottom of the ocean and will supposedly keep him trapped there forever. One only has to stick an ice cube in water to see the problems with this.
- A better possibility is that, while the ice might thaw, it probably won't happen until it's reached the ocean floor. Which, depending on how deep it is, may mean that there's so much pressure that Walker won't be able to move.
- Continuity Cameo: Rossum has a robot of Bat-Mite. And he is just as annoying as the actual character. Interestingly, Paul Dini would later write a Bat-Mite based episode in Batman: The Brave and the Bold. In the background, you can also see robots of Streaky The Supercat, Krypto the Superdog and Mr Mxyzptlk with Silver Age designs.
- Characterization Marches On: In "Heart of Ice", Victor was a pun-spouting, gloating, cruel villain who only cared about himself, with sympathetic motivations and a sad ending. This is the episode that brought about the characterization fans remember; a stoic and reserved Woobie who just wants to be left alone with his wife and has more empathy than he'll admit.
- Corrupt Corporate Executive: Walker wants a world without anyone he doesn't approve of, where everyone has to obey him.
- Cute Machines: Karl Rossum has gone back to building toy robots to keep him company (albeit not as complex as H.A.R.D.A.C.), one of which is a Shout-Out to Bat-Mite.
- Cybernetics Eat Your Soul: Mr. Freeze's denouncement of Walker's Immortality Seeker goal.Walker: Look at me, Mr. Freeze. I'm an old man. I've created wonders in my lifetime, but there is still so much to do. I want to change as you have. To become, like you, a being of blessed, eternal cold.Freeze: You're insane.Walker: Only you know how to duplicate the accident that made you what you are. What I long to become.Freeze: You want to live like this? Abandoned and alone? A prisoner in a world you can see, but never touch? Old and infirm as you are, I'd trade a thousand of my frozen years for your worst day.
- The Dragon: Freeze briefly becomes one to Grant Walker.
- Evil Counterpart: As pointed out by a reviewer, Walker and Freeze stand in deliberate contrast to each other. Freeze claims to be dead to emotions, but his compassion betrays him several times during the episode: he at first refuses to subject Walker to the same confinement as Freeze himself, and Batman eventually convinces him to help stop the deaths of innocent people. By contrast, Walker is an outwardly warm, paternalistic figure, but he is as dead to emotions as Freeze claims to be, coldly planning mass murder just to create his own fantasy of a perfect world. His transformation into "the second Mr. Freeze" is more appropriate to his inner self than Freeze's ever was. He is a rare example of a evil counterpart to a villain.
- The Evils of Free Will:Walker: My world will have no crime, violence, or pain.
Robin: You can add free will to that list, too!
Walker: A small price to pay for order.
Batman: Your order. For your select few!
Walker: Excuse me, but I fail to see the problem with that.
- Expy: Grant Walker could be described as "Evil Walt Disney".
- HeelFace Turn: Mr. Freeze frees Batman and Robin and helps them stop Grant Walker when Batman reasons that even if he succeeds in curing Nora, she will be ashamed of how he did so.
- An Ice Person:
- Mr. Freeze (naturally)
- Grant Walker becomes this after Mr. Freeze recreates the accident that created his condition.
- Immortality Seeker: Grant Walker kidnaps Mr. Freeze so he can replicate the accident that turned him into An Ice Person, as it dramatically slows down the aging process.
- Knight Templar: Grant Walker. He plans to make a crime-free utopia and freeze the world, thinking it's too corrupt to survive. Granted, In Gotham's case he may have a point there.
- Meta Casting: William Sanderson playing Karl Rossum, who had already become a near-Expy of J.F. Sebastian in the H.A.R.D.A.C. episodes.
- Morality Chain Beyond the Grave: Batman convinces Freeze that if he helped Walker destroy the world in exchange for a cure for Nora, she'd hate him after she found out what he'd done.Batman: You think you're alone now? Wait until she learns the truth!
- Mr. Alt Disney: Grant Walker. A pioneer on animatronics and amusement parks owner, his design of an underwater utopia with no crime is loosely based on the original concept for Epcot Center. He also wants to be frozen like Mr. Freeze, a clear gag on the urban legend that Walt Disney is in cryogenic storage.
- Not Quite Dead: This episode reveals that Nora Fries was not killed in the accident that transformed Victor as had been believed in "Heart of Ice" but instead had Victor's experimental cyrogenetic chamber put her in suspended animation before Walker eventually bought it from GothCorp.
- An Offer You Can't Refuse: Grant Walker pulls on Mr. Freeze when he initially refuses to help:Mr. Freeze: Old and infirm as you are, I'd trade a thousand of my frozen years for your worst day.
Grant Walker: Actually, I had another kind of swap in mind. (Promptly reveals Mrs. Fries who, until then, was thought to be deceased)
- O.O.C. Is Serious Business: This was how Batman knew Freeze wasn't behind his breakout of Arkham:Batman: (watching a video of Freeze's breakout) Look at the expression of fear on his face. That's not easy to fake, especially for a man claiming to be dead to emotions. Freeze was taken against his will.
- Pre-Mortem One-Liner: Done by Mr. Freeze to Grant Walker before freezing him in a block of ice:Mr. Freeze: You may live forever, Grant Walker, but your mad dream dies now.
- Sean Connery Is About to Shoot You: Mr. Freeze fires his freeze gun directly at you. In the commentary, the directors are surprised they got away with it — they wouldn't have been able to with a regular gun, in case some kid decided to try it.
- Shout-Out: The robots in the opening are based on Castle in the Sky.
- Silence, You Fool!: Mr. Freeze snaps at Batman when he points out that Nora would hate what he's doing, but in the end he can't shut out the truth and decides to help Batman and Robin stop Walker.
- Small Role, Big Impact: Grant Walker may have massively failed to create a frozen utopia, but he did put Mr. Freeze back in business by giving him the motivation to save Nora instead of just seeking revenge. Had he not found her, Victor's criminal career would've been much shorter.
- Take That!: Possibly. The villain is obviously based off of Walt Disney, this show is made by Warner Bros. who is one of Disney's biggest rivals.
- Utopia Justifies the Means: Walker seems to believe that freezing everyone on the planet except for his chosen few will help to create a better world.
- Who Wants to Live Forever?: "Deep Freeze" states that, even if he's not immortal, Freeze's condition slows down his aging process and he can likely live for thousands of years. And he wants none of it.
- You're Insane!: Mr. Freeze has this response to Grant Walker's plan to freeze the entire world except for his own island. When a supervillain is the one doubting your sanity, you know you have problems. Better yet, an ice-obsessed villain saying this about a plan to freeze the world. (Of course, this has a great deal of Fridge Brilliance, pardon the pun. Freeze considers his condition a Fate Worse than Death, but Walker actually wants it, causing Freeze to regard him as mad. As Freeze himself tells him:Freeze: You want to be like this? Trapped in a world you can see but never touch? Old and infirm as you are, I would trade a thousand of my frozen years for your worst day.