San Francisco was transformed into Gotham City for a day as leukemia survivor Miles Scott became superhero 'Batkid' and battled with villains to clear the streets of crime.
Miles was ferried from the city's Union Square in one of two Batmobiles yesterday morning to begin a series of missions that would take place throughout the day.
The five-year-old had been told that he was being taken to San Francisco just to get a Batman costume.
Instead, he was called into service as 'Batkid' by Police Chief Greg Suhr in a megaphone broadcast and spent the day zooming from one 'crime scene' to the next.
Batkid's crime-fighting missions included rescuing a woman tied to explosives on cable car tracks, catching the Riddler as he robbed a down town bank and stopping Penguin in his attempt to kidnap the San Francisco Giants baseball team mascot Lou Seal.
The US Justice Department even prepared an indictment for the arrest of Riddler and Penguin.
The day was organised by the Make-A-Wish Foundation, who worked with volunteers and city authorities to block off roads and create staging areas to make Miles' wish of becoming Batman a reality.
He was diagnosed three years ago, has undergone chemotherapy treatment and is now in remission.
Make-a-Wish also recruited flash mobs to signal when Miles was to deal with another crime and thousands followed the five-year old with 'Batkid' signs bearing 'my hero' slogans.
The charity received so much attention on Friday as the day played out their website crashed and they were left apologising to supporters for the technical difficulties which they blamed on increased traffic and "a few troublesome villains".
Miles' efforts to rid San Francisco of crime were duly appreciated by US President Barack Obama, who expressed his gratitude in a Vine that said: "Way to go Miles, way to save Gotham".
His stunt as Gotham's superhero caught the attention of the nation and Miles can now count celebritys such as Britney Spears and rapper Macklemore among his fans, with Spears tweeting: "Awww this makes me smile! Miles really is a superhero and inspiration to all".
As Batkid, Miles had a police escort as he sped around the city in a black Lamborghini with a Batman decal, with officers blocking traffic and riding alongside him on motorcycles. The White House sent out a tweet encouraging Batkid to “Go get 'em!”
After making the streets of San Francisco safe again, Miles was handed a key to the city by Mayor Ed Lee.
The San Francisco Chronicle, who live blogged the events, has said it plans to distribute special edition newspapers featuring the headline "Batkid Saves City," in Union Square.
Miles' father Nick Scott thanked the thousands gathered, organisers and the city for making his son's day so special. “This is closure for us,” he said. “It has been a hard three years.”