My example for Ruby #irc showing how you can contort and mixin class methods.

class_mixin.rb

require 'digest/md5'

class_name = Digest::MD5
module class_name::Mixin
end

class_name::Mixin.class_eval do
  class_name.public_methods(false).each do |method_name|
    define_method method_name, class_name.public_method(method_name).to_proc
  end
end

# Example usage
include Digest::MD5::Mixin

p hexdigest 'foo'