Module "inheritance" and ancestor tree.

animals.rb

module Fishish
  def kind
    "fish#{super}"
  end
end

module Dogish
  def kind
    "dog#{super}"
  end
end

module Catish
  def kind
    "cat#{super}"
  end
end

class Animal
  def say
    puts "I'm a #{kind}!"
  end

  def kind
    " animal"
  end
end

class Dogfish < Animal
  include Fishish
  include Dogish
end

dogfish = Dogfish.new
dogfish.say # => "I'm a dogfish animal!"

p Dogfish.ancestors # => [Dogfish, Dogish, Fishish, Animal, Object, PP::ObjectMixin, Kernel, BasicObject]