"I've never seen anything go viral like this, with the outpouring of support from across the world," said Patricia Wilson of Make-a-Wish Foundation, the charity which organized the dream day.
Thousands gathered in the city's Union Square when the Batkid took a break to refuel at a local restaurant. "Even superheroes have to have lunch," explained one TV reporter, surveying the throng stretching across the square.
The city's San Francisco Chronicle printed a special edition for, with a "Gotham City Chronicle" masthead and a screaming headline: "Batkid Saves City!"
The US Attorney's office put out a spoof press release -- datelined "San Francisco/Gotham" -- announcing that the Riddler and the Penguin had been charged with conspiracy and kidnapping.
"Duo faces long prison terms thanks to Batkid," it said.
In Washington, Obama released a message via the Vine video sharing service, looking into the camera and saying "Way to go, Miles! Way to Save Gotham City."
The First Lady added, on her Twitter feed: "Thanks for catching all those bad guys #SFBatKid! You're an inspiration to us all. -mo"