prepend.rb

module Plugin
  def some_method
    puts "Plugin"
    super
  end
end

class A
  def some_method
    puts "A"
  end
end

class B < A
  prepend Plugin

  def some_method
    puts "B"
    super
  end
end

class C < B
  def some_method
    puts "C"
    super
  end
end

C.new.some_method