(WMAQ) -- The 12,000 volunteers who donned superhero capes and morphed San Francisco into Gotham City can't make sure a California boy will stay clear of leukemia for the rest of his life.

But, in handing the 5-year-old the key to the city on Friday, they sure gave him every boy's dream-come-true for a few hours and a memory for a lifetime.

After the Batphone rang at the Grand Hyatt hotel, Miles – a shy kindergartner with bright blue eyes who is in remission from his cancer – became "Batkid," complete with mask, cape and puffy fake muscles. Wearing Velcro sneakers, Miles exited the Batmobile, but only after unstrapping himself from his car seat. (Safety first, Robin.)

"He's just the cutest," said Jackie Johnston, one of the hundreds of fans who had come out to watch.

But Miles isn't just cute. He's a cancer survivor. And in the eyes of the world, he's a hero.

He jumped on a trampoline to give him a little extra boost and untied a "damsel in distress," sitting on the cable car tracks on Hyde Street, a green bandana wrapped around her mouth and a plastic box of what looked like explosives strapped to her back. Of course, the 5-year-old didn't know exactly what to do at first but was aided by his partner in good deeds, Batman – one of the many volunteer actors participating in the event.

The crowds went wild, cheering clapping and ringing bells.

"He's great, he did such a great job," Mario Martinez said, holding his own son in his arms.

After that caper, Batkid went on to apprehend the Riddler, chase the Penguin, and stop at Burger Bar in Union Square to fuel up. And then, like every good superhero does - he was poised to accept the key to the city from the mayor, in this case, Ed Lee.

Miles, whose last name has not been given, has been a bit shy about talking through all this – a dream-turned-reality – thanks to the Make-A-Wish Foundation in the Bay Area, an organization that grants children with life-threatening illnesses their wishes. In some brief interviews before his big day – which had been a surprise – Miles simply said his wish was to Batman, a character he regularly slips into during his rough-and-tumble escapades where he lives in Tulelake, Siskyou County, near the Oregon border.

But his mom, Natalie, who also didn't give her last name, said this dream is emblematic of her son's battle with leukemia.

"He likes to be a superhero," she said. "He is one. He beat an awful disease."

All this is happening because of what happened after Patricia Wilson of the Make-A-Wish Greater Bay Area Foundation sent an email in October asking for some volunteers to help give Miles his wish.

The email went viral, and between 11,000 and 12,000 volunteers came to contribute their efforts, whether it be acting, being stage crew or assisting in a myriad of other ways. The Make-A-Wish Foundation in the Bay Area has been operating since 1984, when it was able to grant 27 wishes. Now one of the largest chapters nationwide, foundation grants 300 wishes per year and 6,000 wishes in all.

"Obviously, we'll never replicate this," Wilson said. "This is a moment in time when something goes viral and the city goes alive."