Rachel's (Tatiana Maslany) quote about cutting lab rats' tails is a subtle reference to the works of August Weismann. In the late 1800s he determined that regardless of how many generations of mice had their tails cut off their offspring had normal length tails.
The board game that Krystal (Tatiana Maslany) attempts to play with Scott (Josh Vokey) and Hell-Wizard (Calwyn Shurgold) is "Dead of Winter", and it is a semi-cooperative game with the players representing survivors of a zombie apocalypse. Although the players cooperate to some extent, they must complete their own secret objective to win and an experienced player would not just give away their resources like Krystal did.
For her "camp" look, Evelyne Brochu (Delphine) went almost completely without makeup for episode 4.9, The Mitigation of Competition (2016), and episode 4.10: From Dancing Mice to Psychopaths (2016). Producers also thought it was time to bring back some of her infamous curls, for practical and realistic reasons and for the Cophine fans.
Clone Count 5: Krystal, Rachel, Cosima, Sarah, Helena, (6 counting Alison who was in the extended scene only). All are played by Tatiana Maslany.