The stars of Marvel’s super-hero franchises have been seriously gracious of giving their time to kids. Chris Pratt and Chris Evans visited two children’s hospitals over a bet during last month’s Super Bowl.

Now we have RDJ presenting a 7-year-old with a robotic prosthetic limb made to look like Iron Man’s– and he did it in character as Tony Stark. Check out that video below!

The prothetic is actually designed by UCF Aerospace Engineer Albert Manero who printed it out using a 3D printer and uses off the shelf servos and batteries for less than $350.

The problems with creating a robotic limb for children have to do with miniaturization of the components and because they grow quickly, most insurance companies won’t pay for them because the prosthetics will need to be replaced several times.