Howard's ringtone is "She Blinded Me with Science," which was the theme song for the show's original, unaired pilot.
Leonard and Raj hire a prostitute named Mikayla (played by Jodi Lyn O’Keefe ) to pose as a Jewish girl named "Esther Rosenblatt" to cheer him up.
Howard eventually realizes she’s a professional but, instead of being offended, is deeply touched that his friends would do that for him and continues the "experience". Sheldon's "Fortress of Solitude"
Back in Pasadena, Sheldon plans a glorious weekend of being alone, eating Indian food that the others can't have due to allergies or personal distaste (paneer).
His plans are ruined when he realizes he left his keys inside the apartment. With the building manager unavailable, he is forced to seek shelter with Penny.