Trivia: In this episode, Sheldon and Amy are trying to decide on couples' themed Halloween costumes. Sheldon is standing in front of the dry erase board. There are 2 columns written on the board. One named "Couples I Like" and the other "Couples You Like." Under the "Couples You Like" column, one of the couples is Blossom and Joey. Blossom is the name of the television character played by Mayim Bialik in the 90s and Joey was one of her brothers.
Trivia: In the beginning, after talking about the Spider-Man theme, Sheldon says it's right up there after Inspector Gadget and Teenage Mutant Ninja Turtles (to which the gang chimes in "heroes in a half shell, turtle power"). Chuck Lorre, the show's creator, wrote the original TMNT theme song that they are referring to.
Trivia: When Leonard, Howard and Raj are contemplating who to have as the fourth member of their Physics Bowl team, Raj says, "You know who's apparently very smart is the girl who played TV's 'Blossom'. She got a Ph.d in Neuroscience or something." The girl he's referring to is actress Mayim Bialik, who plays Amy Farrah Fowler in later episodes of The Big Bang Theory. Interestingly, she is the only recurring cast member on the show that actually does have a Ph.d in real life.
Trivia: Raj's question about why so many of Stan Lee's characters' first and last names begin with the same initial (Peter Parker, Reed Richards, Bruce Banner, etc.) has been answered by Lee in interviews before: He has a bad memory for names, so if he can remember one of their names, he knows the other starts with the same letter.
Trivia: One of Penny's classmates, Cole, is portrayed by Ryan Cartwright. Ryan Cartwright is a main character on Alphas. At the time of the episode, Alphas hasn't been cancelled. Episode 21, The Closure Alternative, deals with Sheldon getting over learning Alphas had been cancelled.
Trivia: You don't have to be a big The Big Bang Theory fan to know that Sheldon has his spot on the couch, but did you notice that other characters also sit in 90% of scenes on the one spot. Leonard is always on the sofa left to Sheldon, Penny is almost always on the sofa across Sheldon, Howard is always next to Sheldon on the couch (except in situations when Amy or Bernadette sit between him and Sheldon), and Raj is always on the left side of the couch (viewers' left), or on the floor.