Iron Man backs Aaron Hunter's Muddy Puddle Challenge

Iron Man and Avengers star Robert Downey Jnr issues "muddy puddle challenge" to his fans in support of a terminally-ill Scottish boy.

The Hollywood actor posted a video of himself wearing a "See You Jimmy" wig and jumping in a muddy puddle.

Downey Jnr then introduces Aaron Hunter, from West Dunbartonshire.

The eight-year-old started the challenge to raise awareness of his rare illness called ROHHAD, for which there is no cure.