Batman was played by Lewis Wilson who may have looked like Bruce Wayne but in his Batman costume he looked closer to Adam West. The serial made several changes that weren’t in the comics but later affected the comics. He initial didn’t have one in the comics but in the serial Batman had a Batcave, complete with a secret entrance through a clock. That later become part of the Batman mythos. In the movie Alfred was a skinny butler with a mustache but in the comics he was a fat clean shaven butler. After the movie came out Alfred ended up losing some weight.
There were a couple of changes that didn’t happen in the comics. Because of the budget constraints of the serial, there was no Batmobile or any bat-gadgets. Just a black limousine that Alfred chauffeured both Bruce Wayne and Batman around in (funny how nobody noticed that Batman had the same chauffeur as Bruce Wayne.) And because of the production code at the time, Batman couldn’t be a vigilante, here he and Robin are special FBI agents.
This serial pitted Batman and Robin against the usual WWII suspects, the Japanese and being a wartime propaganda piece, it’s fairly racist. The film was popular enough that it spawned a sequel in 1949 but Robert Lowery took over for Batman with about the same success as Lewis Wilson had.