Proof of https://twitter.com/pixeltrix/status/547291696032411648

santas_list.rb

class Kid
  attr_reader :name, :naughty, :nice

  def initialize(name, options = {})
    @name    = name
    @naughty = options.fetch(:naughty, false)
    @nice    = options.fetch(:nice, false)
  end

  alias_method :naughty?, :naughty
  alias_method :nice?, :nice
end

kids = [
  Kid.new('Alex'),
  Kid.new('Isobel', nice: true),
  Kid.new('Phoebe', naughty: true),
  Kid.new('Nathan', naughty: true, nice: true)
]

2.times do
  kids.select!(&:nice?)
  kids.reject!(&:naughty?)
end

puts "Santa's list is #{kids.map(&:name).join(', ')}"

santas_list.rb output

$ ruby santas_list.rb 
Santa's list is Isobel