I just made this up, don't know if it's funny What did the impotent atheist say after taking Viagra? Kerrist...its risen!
I guess it would have been more apt at Easter. Then again maybe not. I'm just so used to people in my country saying 'Christ is risen', on Easter day; perhaps they don't say that outside the Christian Orthodox religions. In fact what happens is that one person says Christ is risen to another and the other one replies, the Lord is true.