From one of Batman's worst villains to one of his best, fantastic.
In "Christmas with the Joker," The Joker takes over the airwaves with his own version of a Christmas special, complete with surprise guest hostages and a wild goose chase around Gotham for Batman and Robin.
And yes, it's THAT version of Jingle Bells, which comments on Batman's body odor and mechanical trouble for his car, which also demonstrates the Joker's meta-awareness, the fact he seems to know that he's a fictional character in a TV show, like when he provides his own title card for the episode, or tells us the show will be right back after a word from the sponsor, right before the commercial break. Is he crazy? Or is he hyper-sane?
Outside of Batman himself, the Joker is probably the best character in the Batman mythos, and definitely the best in the cartoon series. The Joker first appeared in Batman #1, and has had many different interpretations over the last 70 years; crime boss, serial killer, colorful bank robber, terrorist, anarchist, nihilist. Like they did with Batman, the producers of the series drew on all of these versions, but instead of synthesizing it down to one cohesive whole, they just left it all in, hodge podge, creating a character that veers wildly from clown to killer between episodes, and even within them.
All of which is brought forward by Mark Hamill incredible voice work: his manic laughter, enthusiastic deliveries, underlying malice and his mercurial mood shifts from delight to hatred to boredom to actual fear to sheer delight again. Hamill's Joker actually seems to be having a good time. (Something I think Nicholson's Joker didn't have, and Ledger's Joker sometimes had).
This episode also establishes that, while Joker wouldn't mind killing Batman, he'd much prefer to keep him alive and focused on him. At two points, the Joker basically wins, and so he must give Batman a hand. When Batman is lost and cannot find the Joker's base, the Joker gives him a clue where to find him. When he has Batman at his mercy, instead of blowing Batman up or dumping him in acid, he throws a pie in Batman's face. So from his first episode, we see that the Joker could never really kill Batman, or he'd lose his favorite audience member. And God help anyone else if THEY managed to kill Batman (but that's an episode we'll get to later).
The Joker serves another purpose, the ever-present threat. The first third of the episode, where Robin tries to convince Batman to stay home and watch It's a Wonderful Life because no one commits crime on Christmas, resembles a Batman short story, "The Silent Night of Batman," where Batman spends the night singing with the police choir as the people of Gotham basically sort out their own problems for once.
Robin is also first seen in this episode, but like the Joker, he isn't introduced as much as assumed to have always been there. To be clear, this is Dick Grayson, the first Robin, though he's wearing Tim Drake's uniform, long pants, black cape with yellow interior.
His relationship to Batman, however, is firmly established. In the field, he's junior partner. Batman gives the orders, but trusts Robin completely to carry them out. They even have established plays they can call in the field. (Though it seems "Operation Cause and Effect" means "stop whining about the Joker robots and blow up the cannon like I told you.").
At home, however, Robin is family. When later episodes establish Dick is attending college, we realize he's home for Christmas, and that's why he's disappointed to spend it with Batman "at the office." The show brings up that the Joker doesn't have a family twice, to contrast it with Batman, who though he may not realize it, does.
This episode places the show in a very odd place, time wise. For the most part, we're supposed to be seeing Batman's early career. This is his first encounter with most of the villains (other than the Joker and the Penguin), the police don't trust him, and Harvey Dent is still good looking. But his line, "it's never easy with the Joker," implies that he's fought the Joker many many times.
Robin's age also implies Batman's been Batmanning for a while. Assuming Batman didn't adopt Dick right away, and seeing that they are practiced partners by now, we have to assume he's been at it for four or five years at this point. Which makes it somewhat odd that the police still don't trust Batman, and Batman STILL doesn't work with the police.
Besides the Joker and Robin, this episode also introduces reporter Summer Gleason, a low-rent Lois Lane knock off, as one of the hostages, but she's not named and surrounded by Gordon and Bullock, it'd be easy to assume she was cop as well. We'll get to her a bit more in the next episode.
That Batman hasn't seen It's a Wonderful Life, the story of how much good one man can do for a city, because he couldn't get past the title, is fantastic character work.
The animators are also zeroing in on the period setting. The television sets are still in color (later they'll be exclusively in black and white), but the hoods are now using tommyguns and the cameras look like something from the fifties.
And finally, I have long argued that Batman has one of the best dressed Rogues Galleries of any superhero. It'd be easy to wear tights and battle armor, but most of Batman's villains wear suits and tuxedos. It's a shame the first episode with the Joker doesn't have his purple zoot suit, but the green turtleneck under the orange cardigan (with optional breakaway hands) IS delightfully festive.
And so, in all, a great introduction of Batman's chief antagonist, their ongoing struggle, and Robin to boot. A Christmas miracle!