In spring, hence now, robins return. Ergo, from whose mind was Robin the Boy Wonder sprung?
When I passed along excerpts from articles and interviews addressing Robin’s creation to Robin-N-More blogger J.L. Bell, he synthesized a characteristically thoughtful post about it.
My conclusion nearly overlaps with J.L.’s. I believe Bill Finger most likely came up with the idea for a sidekick (though Kane took full credit and Finger himself modestly categorized Robin as a “group” creation), early Batman ghost artist Jerry Robinson was responsible for the name (inspired by Robin Hood, not himself) and costume, and Finger crafted the origin. J.L.'s theory that an editor suggested making the sidekick a boy seems plausible, though I rarely rule out Finger.
Finger was the primary Batman writer at the time, so even casting aside the particular personalities involved, it just makes sense that he’d be the one to start a campaign for a partner (no matter the age). It’s not easy to write a solo character. Even the marooned man Tom Hanks played in Cast Away had a volleyball to talk to.
Among the various interviews in which Robinson gives Robin credit to Finger, my favorite is from Alter Ego #39 (1/03). In that, Robinson said he is “positive” Robin was Finger’s idea. Of course, memory isn’t infallible, but Robinson is one of the few still alive with the authority to be trusted.
In a 1989 magazine publication called Comics Interview Super Special: Batman—Real Origins of the Dark Knight, Kane was quoted as follows: “Robin was mine, it wasn’t even Bill Finger’s” (page 16).
Kane probably didn’t realize that his “wasn’t even” was both defensive and revealing. It seems that Kane’s conscience was admitting that so much of Batman was Finger’s while his ego was holding on to the idea that at least this component (a significant one, of course) was Kane’s.
In that same publication, Kane was also quoted as saying, “I came up with Riddler and Joker, maybe Penguin was mine—time erodes memory” (page 17). I'd wager it was not time affecting memory but rather intentional manipulation, with that breezy "maybe" thrown in to diffuse the disreputable nature of Kane's brazen and perpetual idea-grab. That said, I do allow that there may have been a small degree of truth in Kane's statement, at least in his own mind, because memory (as mentioned above) is indeed notoriously unreliable.
In either case, various sources suggests that none of these three classic villains came from Kane. It’s a subject for other posts, but in short, I believe that Joker was a co-production of Finger and Robinson while Finger alone has been credited for the concepts of both Penguin and Riddler.
Kane had an explanation for where he got the idea for Penguin, but Finger’s son Fred (among others) said the character came from Bill—and of Kane and Finger, only one was known for stretching the truth when it came to credit.
As for Riddler, no less respected an editor than Julie Schwartz gave Finger credit for Riddler—in print and in a Batman comic, no less (Batman #169 [2/65]).
This was while Kane was still alive.
Poignantly, while Finger was, too.