Batman: The Animated Series: 10 Best Characters Who Only Appeared In One Episode

Mr Freeze-centric episodes are always a highlight of Batman: The Animated Series, with "Deep Freeze" being no exception. However, while Freeze is the highlight of the episode, the villainous Grant Walker also shines in his only appearance in the series.

Walker is an aging tycoon, who wishes to see the world become as joyful and peaceful as one of his amusement parks that he owns. He is willing to do this by any means, but believes that he will die before he can finish his plans.

This results in him kidnapping Victor Fries/Mr Freeze, forcing him to recreate his accident so that Walker can become like him. While Freeze objects, the sinister Walker uses Freeze's wife Nora as bait - claiming he has the means to save her if Freeze does his bidding.

Victor complies and Walker becomes exactly like Mr Freeze, eventually conjuring up a plan to freeze the world. This is due to Walker seeing the world as corrupt and horrible, and the only way to fix this is by freezing the planet and wiping out everyone who is not within his Oceania theme park.

Batman and Robin eventually help Mr Freeze see reason, and the three stop the villain, with Walker being left frozen in a block of ice for all of eternity. Truly, a fitting fate for a sinister man.