|He's shocked because he just saw the Bob Kane signature and he knows there's no way he had anything to do with this comic.|
Debuting in Batman vol.1 No.90 (March 1955, "The Adventures of Batboy!"), the Dynamic Duo meet this diminutive daredevil while getting their asses handed to them at a factory which makes baseball bats. I don't know if it's superior numbers or mere irony which overcomes the Caped Crusaders, but Batman and Robin are in dire need of rescuing after an assault by the henchmen of notorious crook and star of a famous beer-pouring game, Tapper Nolan.
|It's corked like a motherfucker.|
In short order (haha again, see below), Bat-Boy has managed to outfit himself with a snazzy costume (catcher's mask, baseball uniform and a cape, for flair!), an underground headquarters dubbed The Dugout, and a small armory of trick baseball bats: A Baseball Bat-arang, a Parachute-Bat, a Porcupine-Bat which shoots quills (let's take a moment and let that one sink in), and a Web-Bat which is a bat with a net in it, and probably it would have been easier just to throw a net on someone. The genuine takeaway from this is that it apparently doesn't take a millionaire's resources to build yourself a crimefighting base. Any little kid with a Louisville Slugger and a burning hatred for crime can do it!
Robin and Bat-Boy find an opportunity to pursue Tapper Nolan's gang together (thanks to an improvised Baseball Bat Signal), and Robin's keen detective skills assist the boy crimefighter in deducing Bat-Boy's weird secret: He's not a boy, he's a circus midget! Formerly a performing acrobat in an ill-fated circus, the other two members of Bat-Boy's (aka Midge Merrill, and I'm assuming "Midge" is a nickname and not his parents rubbing it in) tumbling trio are murdered when Tapper Nolan, then a roustabout, sets fire to the big top and leaves everyone inside to burn while he swipes the gate receipts. That is ... that is genuinely horrible to think about.
|And you're judgmental!|
Midge gives up his crimefighting identity once Nolan is put away, for possibly the best reason in comics history. "Now that I've caught up with Tapper, the ambition to go on as Batboy is gone!" he tells the Boy Wonder, adding "Besides, a guy my age gets tired too easily!" You and me both, brother.
Robin arranges for Midge to pick up a second career as an actual bat-boy for the very team whose hitter was endangered by the explosive baseball bat, which can't possibly pull in a living wage for a middle-aged man. Never mind merely making ends meet, he still has to pay off the presumably massive loan he took out to afford an underground crime-fighting HQ and an arsenal of gimmicked bats. Luckily he's working in professional baseball now, so there's always a little money to be made in acting as a drug mule.