array_flatten_1.9.2_part_2.rb

class Foo
  def method_missing(method_name, *args)
    return if method_name == :to_ary
    # ...
  end
end

# Running above benchmark
#                            user     system      total        real
# flatten Object objects  0.000000   0.000000   0.000000 (  0.014153)
# flatten Foo objects     0.060000   0.040000   0.100000 (  0.094241)