When Leonard first sees Sheldon's new collection of cats and Sheldon introduces the cats to him, the all-white cat is introduced as Dr. Richard Feynman. Shortly thereafter, when Sheldon introduces the cats to his mother, the cat introduced as Feynman is the ginger one, not the white one.
In the cafeteria, the snacks in the snack machine change. Note the candy bar, which is leaning one way, but later in the scene is leaning the other way. Watch Amy's hair when she is talking with Sheldon. From behind, her hair is caught up in her collar. From in front, her hair is outside the collar.
In the last shot of Sheldon and Amy disposing of the cats, the "Cats $20" sign has been replaced by a digital graphic inserted into the video. The real sign has creases similar to the tablecloth as we see in previous shots, but in the last shot the sign is devoid of any three-dimensional effects.
When Sheldon introduces the cats to his mother, the cat toy on the bed moves around between shots.
In the laundry room Penny takes the same item of clothing from her basket and puts it in the machine twice.
Mrs. Cooper says her brother Stumpy's original name was Edward. However, in the earlier chapter "The Cruciferous Vegetable Amplification", the chart showing Sheldon's family tree gives her only sibling's name as Carl. However, as anyone familiar with Southern familial naming practices would be aware, a person's given name is not automatically how they are addressed--nick names, family anecdotes, and even middle names often dictate the familial name used.
When Amy and Sheldon "break up", before they arrive at the table, Raj is sitting on the end of the 4 person table. He would only do this if they were saving the other two seats for someone else. When Sheldon and Amy enter the scene, the guys seem to have not been expecting them.
Sheldon and Amy are playing a made up game where they state that "In a world ruled by a giant beaver, mankind builds many dams to please it, the low lying city of Copenhagen is flooded..." The city of Copenhagen is located on an island off mainland Denmark and on the coast so damming rivers would never cause it to flood.
Sheldon winds up with 25 cats. However, in Season One's "The Fuzzyboots Corollary", he is thoroughly upset when Leonard indicates he is getting a cat, thus indicating Sheldon doesn't like cats. Leonard also mentions that Sheldon has asthma. And in Season Three's "The Plimpton Stimulation", Sheldon states that pets are banned according to the roommate agreement.
It's possible that Sheldon considers cats emotional support animals, which many people erroneously consider service animals; therefore they would not be banned under the roommate agreement.
It's possible that Sheldon considers cats emotional support animals, which many people erroneously consider service animals; therefore they would not be banned under the roommate agreement.
Amy states (and Sheldon agrees with her) that the danish is a pastry invented by the people of Denmark. They were actually invented in Vienna.
Whilst playing a game with Sheldon and Amy Leonard proposes that in a world where beavers are our overlords the B in BLT would stand for beaver. Leonard is a genius who knows Sheldon very well and would know that such a stupid and inept response would be met with disdain and ridicule.