Iron Man Robert Downey Jr surprises 7-year-old boy with new bionic arm

Robert Downey Jr reprised his role as Marvel superhero Iron Man to personally deliver a bionic limb to a child with a partially developed arm.

Seven-year-old Alex, who likes superheros and riding his bike, was the lucky recipient of the gift as part of the Collective Project - the brainchild of college student Albert Manero.

Manero, who builds and donates low-cost, 3D-printed bionic limbs to kids around the world, was able to pull off the stunt with the help of a leading bionics expert.

Alex appeared remarkably chilled out about meeting Downey Jr, whose Iron Man character employs numerous robotic limbs.

Downey Jr seemed almost as thrilled as Alex about the meeting, tweeting several photos of the moment.