What Planet is He On?

I know Robbie can be a bit random at times but on Friday evening he looked up from his laptop and started talking about the Clangers and why they didn't fall off their planet. I have considered many questions about the clangers over the years but I have never given the atmospheric conditions of their (imaginary) planet. I have wondered how Major Clanger acquired a military rank when the clangers do not have an army and I gave more than a passing thought to the soup dragon's reproductive habits, apparently there was only one soup dragon so where did the baby soup dragon come from? I was very tempted to tell him that being knitted allowed them to cope with the sparse atmosphere of their planet, but I know Robbie too well and such a comment would have led to him talking about Clangers all weekend. So I just asked him what made the Clangers pop into his head, he explained that one of his friends had commented about it on facebook, apparently her son had asked why Clangers don't fall off their planet. Obviously kids go for the easy questions these days. When Sam was little he liked to watch Coronation Street with his Grandma and one day he asked "How did the doctors make Hayley into a girl?" I would have preferred a nice safe question about the Clangers!!