When his character in Casualty, Richard McCaig, was diagnosed with Multiple Sclerosis Gray decided to get involved with the MS Society, and raise money for them.
He once took part in a 17 mile walk to raise money for the British Heart Foundation.
Gray has appeared on 'Lifeline' in an appeal to help the organisation 'Combat Stress'.
He fell over a fence, at the age of 15, resulting in two broken wrists and all the bones in one hand being broken too.
His favourite music is the 'Cocteau Twins'.
Gray was nearly thrown out of drama school in his first term, for asking too many questions. He did a deal, however, he could stay if he kept quiet.
Gray O'Brien: (on himself) I am just a jobbing actor from Scotland and I don't think of myself as particularly good looking.
Gray O'Brien: (talking about his fan mail) I don't even read the fan-mail - not any of it. I think it gives you a false sense of security.
Gray O'Brien: (on his sex symbol status) I also think this sex symbol thing is nonsense - and so does she (his wife) .. I actually find the heartthrob thing laughable.