During the argument between Howard and Bernadette, the apartment flag on the refrigerator is seen upside down, indicating that the apartment is in distress.
When Raj tells Leonard and Sheldon that he and Howard spent the night "giggling, eating cookie dough, and watching The Princess Bride (1987)," Howard tells him to stop talking. Raj replies, "As you wish". "As you wish" was Wesley's standard reply to Buttercup in the movie 'The Princess Bride', and it was revealed in the movie that every time Wesley said it, what he meant was "I love you," and the narrator adds that Buttercup realized she loved him, too. This is another veiled reference to Howard and Raj's friendship that Leonard's mother called an "ersatz homosexual relationship."
Amy's apartment number is 314. The value of Pi is 3.14.
Sheldon displayed a similar dislike to lamb in The Agreement Dissection (2011) when the group made him eat Greek lamb kabob (which he described as "little cubes of charred meat that taste like sweat").
Sheldon (Jim Parsons) says that Sweden is home to his favorite Muppet, which must be the Swedish Chef. Parsons played the human version of Muppet himself in The Muppets (2011).