If you look closely at Sheldon's Facebook page, his Facebook profile picture is the same one of him and the blue jay from the previous episode, The Ornithophobia Diffusion (2011).
Stuart's last name is Bloom (seen on his Facebook page).
First appearance of Sheldon and Amy's Relationship Agreement. There are 31 pages in it, and among its many clauses are sections describing situations in which hand-holding is permitted, and responsibilities in case of injuries ("Booboos and ouchies").
All the Mystic Warlords of Ka'a cards mentioned in this episode have never been mentioned before. This is a running joke throughout the series, mocking the ridiculous complexity of the game, but this is the first time the characters start to realize this.
Amy expresses her contempt for comic books to Sheldon, saying they are "lame-o". However the actress who plays her, Mayim Bialik, has been quoted as saying she was raised on comic books and loves science fiction.