horrible.rb

require 'forwardable'
require 'benchmark'

class Fakenum
  extend Forwardable
  attr_reader :thing
  
  def initialize
    @thing = 1
  end

  def thing_odd?
    @thing.odd?
  end

  def method_missing(method, *args)
    if method == :foobar
      @thing.odd?
    elsif method == :foobaz
      self.class.class_eval(<<-EOD, __FILE__, __LINE__)
      def foobaz
        @thing.odd?
      end
      EOD
      foobaz
    end
  end

  def_delegators :@thing, *(Fixnum.instance_methods - self.instance_methods)
end

fn = Fakenum.new
p fn.odd?
p fn.foobar
p fn.foobaz
p fn.thing_odd?
p fn.thing.odd?

Benchmark.bm do |r|
  r.report('Foo') do
    1_000_000.times { fn.odd? }
  end

  r.report('Bar') do
    1_000_000.times { fn.foobar }
  end

  r.report('Baz') do
    1_000_000.times { fn.foobaz }
  end

  r.report('Fle') do
    1_000_000.times { fn.thing_odd? }
  end

  r.report('Ele') do
    1_000_000.times { fn.thing.odd? }
  end
end

Results

true
true
true
true
true
      user     system      total        real
Foo  0.990000   0.000000   0.990000 (  0.989358)
Bar  0.720000   0.000000   0.720000 (  0.713166)
Baz  0.320000   0.000000   0.320000 (  0.323896)
Fle  0.330000   0.000000   0.330000 (  0.326319)
Ele  0.220000   0.000000   0.220000 (  0.228836)