Before Michael Keaton, even before Adam West, there was...Lewis Wilson? The first actor to have ever played Batman on the big screen, Wilson appears to have had about a two-year film career, and then a bunch of small roles in TV episodes. The career of Douglas Croft, playing Robin, consisted of several roles playing protagonists as young boys, and then a couple of years of playing teenagers in more fleshed out roles, including the Robin role. Ironically, for the supporting cast, that is, the main villain (J. Carroll Naish), the love interest (Shirley Patterson), and Alfred, the trusty butler (William Austin), Batman was simply one entry in their long careers.
But, you ask, what about the freakin' zombies? When did Batman and Robin ever fight those? In this version, the villain, played by Naish, is an evil Japanese spy, Prince Tito Daka. He's developed a process to take over people's minds and control them through a microphone that relays commands to special helmets on their heads. He uses them mostly as lower grade henchman, since his main help comes from self-willed gangsters, but they are zombies nonetheless.
Certainly I wasn't aware of this version of Batman, made as a 15-part serial, until very recently. It's not surprising, since the role of serials from that era seems to be to have been watched once and then remembered in nostalgia. Given the production values of most serials, the best thing they have going for them now is that they're incredibly campy. I recently watched the Flash Gordon serial, which provided no end of staggeringly bad effects and ludicrous dialog. Unfortunately, Batman is fairly mundane in the camp department. The filmmakers were competent with the props they had, and aside from a few fantastical devices like the zombification machine and a deadly gun powered by radium, there's no need to make anything out of the ordinary for the film.
Where the film does stick out is in its incredible racism. Since the film was made in 1943, there is no end of slurs against the Japanese, both on the other side of the war and, sadly, those on our side. In the beginning of the first episode, the narrator refers to the Little Tokyo section of Gotham, which is now mostly empty since "a wise government rounded up the immoral hoods." There is no end of references to "slant-eyes" and "evil Japs", and even "twisted Oriental brains." I've made comments on racism in older films before on this site, but because this was so obviously malevolent, it was harder to overlook. At least with King of the Zombies, the character played by Mantan Moreland was liked and trusted, if not respected, by the other characters in the film.
Yes, there was a plot. Daka has invented a super-gun, powered by radium, and he plans to use it to take over the U.S. The only thing is, he has a hard time finding the radium to power it. He comes up with scheme after scheme for getting radium, only to have Batman and Robin show up and interfere. Daka's henchmen get in a fight with Batman and Robin, do something to Batman that they are convinced will kill him, and then swear up and down to Daka that Batman is finished. Of course, Batman always narrowly escapes whatever fate they had in store for him, sometimes with Robin's help and sometimes without, and the chase continues. It gets pretty repetitive until an old friend of Bruce Wayne's shows up claiming to have discovered a radium mine. Then, at least, there's a subplot that stretches over a couple of episodes.
Perhaps if I had watched this the way it was meant to be watched, in 17 minute segments once a week, I would have had a different experience. As it was, I found myself bored a lot. (Yawn, another fight scene, where nobody actually gets captured or killed.) This isn't to say that there's no interest in the film; it was sort of fun, for instance, watching Bruce Wayne act as the self-centered, lazy playboy to Linda, the love interest. But this was a mostly forgettable experience.