The furthest Batman ever got from being the “dark knight” was the introduction of Bat-Mite, in Detective 267 (May 1959). It’s not too difficult to see how the character came about, he is essentially Batman’s version of Mr. Mxyzptlk, and was created by Bill Finger and Sheldon Moldoff.
Unlike Mr. Mxyzptlk, Bat-Mite is an adoring fan of Batman and Robin, and while his actions prove just as much of a nuisance as the other imp, Bat-Mite’s motives are benevolent, if twisted, in nature.
The first thing he does is make a bridge come to life as Batman and Robin are fighting thieves on it. His powers enable him to do almost anything, and though he is explained scientifically as an other-dimensional creature, his powers may as well be magic.
The good thing about Bat-Mite, in this era, is that he does genuinely succeed at making the stories more interesting, at least visually.
And giant props? Bat-Mite loves them as much as the fanboys do, and he is more than eager to fill an empty warehouse with them, just to make the climactic fight more visually dynamic.
Although it was months before his next appearance, the ending of this story leaves little doubt that the character would return.
John Jones discovers that reports of an alien ship are real, and that the crew of the ship are benevolent Jovians, who have come to Earth pursuing a thief from their world.
J’onn is more than happy to help catch him, especially when the crew agrees to drop him off on Mars on their way back to Jupiter.
J’onn captures the renegade from Jupiter, but at the last minute discovers that he has left a bomb behind, and J’onn stays on Earth to defuse it. Still, his smile in the last panel seems to indicate he is not too broken up by this. Earlier in the story he had shown some reluctance to leave Earth, so it’s safe to say that returning to Mars is no longer the driving goal it was once for the Martian Manhunter.