Twitter users have been calling for the stars of the Marvel Cinematic Universe to complete the “Muddy Puddle Challenge” in aid of the Vale’s Aaron Hunter, eight, who suffers with a rare, terminal illness.

Aaron recently met his hero, Iron Man actor Robert Downey Jr, who shared a video of himself jumping in a muddy puddle and challenging everyone, including his co-stars to do the same and #GOMADFORROHHAD.

The challenge was devised by Aaron himself to help raise awareness of ROHHAD, which causes children to gain weight gain and have breathing difficulties.