Have they been summoned by some sort of . . . bat signal?
In the last two weeks, there have been two incidents of dudes dressed as Batman getting in trouble with the law here in Maryland.
First, hilariously, on March 29th, Lenny B. Robinson, a Baltimore County businessman who has a side gig as Batman, was pulled over as he was driving his Lamborghini "Batmobile" to Georgetown University Hospital. (C'mon, he was speeding to save the children, people! Yeesh!)
Then, on opening day, 26-year-old Mark Harvey stormed the field at Camden Yards dressed as Batman. (The link from Grantland I provided feels legally compelled to say that he apparently ran on the field. Using my crack reporting skills—i.e, my eyeballs—I'm going to go out on a limb here and say he actually ran on the field.)
These sorts of trends obviously come in threes—so we can expect Batman to leave cognac and plastic bats at Poe's grave or mix it up with Kegasus at Preakness.
After that, it's your move, Aquaman!