> Is it possible to do the opposite? call a instance method from a class
> method?

Create an instance and call the instance method; very weird usage
though. Why would you need it?

class Foo
  def self.hello
    Foo.new.hello
  end

  def hello
    puts "Hello World"
  end
end

You can basically call any method from anywhere if you have the right receiver.

-- 
Anurag Priyam
http://about.me/yeban/