At the end of the episode, just as Leonard get's off the phone with Pria you can tell that he's sitting in Sheldon's spot. He never sit's in sheldon's spot.
In this episode, Stewart congratulates Leonard on picking up a girl at the comic book store saying "this is the closest anyone has ever come" and takes a picture of him for a "wall of heroes", however back in season 2 in the episode "The Hofstader Isotope", Stewart himself had similar success with Penny in the comic book store.
The mask that Leonard uses to scare Sheldon is of "Balok", a character that appeared in the Star Trek episode, "The Corbomite Maneuver".
Howard: Who had money on "faints?"
Rajesh: I had "pee his pants."
Leonard: Hang on, looks like everyone's a winner!
Sheldon: (reading 'bloody' wall') "See you in hell Sheldon." The most frightening thing about that is the missing comma!
International Airdates: Czech Republic: June 27, 2012 on Prima COOL; Turkey: October 2, 2012 on CNBC-e; Finland: February 18, 2013 on Sub
This episode's end titles has Chuck Lorre's Vanity Card #363.
While chatting with Leonard in the comic book store, Alice mentions having a "Kryptonian Father". Krypton is the home planet of Superman, a DC Superhero. Courtney Ford, who appears as Alice in this episode, is wife to actor Brandon Routh who is perhaps best known for his portrayal of Superman in the movie Superman Returns.