The Middle-Earth Paradigm is the Halloween episode of The Big Bang Theory.
After the gang gets their butts kicked at paintball, they meet Penny who invites them to her Halloween party. As the party is costumed, the gang is extremely excited. Initially, all four of them dress up as the Flash, so they all agree to change. Leonard calls for Frodo who is everyone's second choice. Leonard asks Sheldon not to embarrass him at the party as he feels this party could be a milestone in his relationship with Penny interacting with her social group.
The gang arrives at Penny's apartment on time while everyone else arrives much later. Leonard is Frodo from Lord of the Rings, Sheldon is the Doppler Effect (which no one understands), Howard is Robin Hood (though everybody thinks he's Peter Pan) and Raj is the Norse God Thor (not the Marvel Comics character). After the party starts, the guys seem left out just sitting on Penny's couch. Howard spots a girl and manages to creep her out. As Leonard wants to talk to Penny's friends, but is afraid to do so, Sheldon becomes his wingman. A girl named Cheryl approaches Raj and talks to him asking him how "wasted" she is, but he still is unable to respond though does react with her.
Suddenly, Penny's ex-boyfriend Kurt arrives at the party. Penny greets him warmly. As they both want Penny, Leonard decides to confront Kurt. After saying Kurt is less evolved than himself and Kurt seems to understand Leonard, Kurt lifts Leonard up intimidatingly. Penny tells Kurt to stop and says that he was just having fun with his little buddy. Leonard is a little shaken up so he and Sheldon leave the party.
Later, Penny feels bad about what happened so she stops by at Leonard's apartment. She gets emotional and claims that she invited Kurt because he was all apologetic, but she can't go back to her party and wonders what is wrong with her. Leonard says that there is nothing wrong and that she is perfect. Penny realizes he feels that way and then kisses him. He stops her advances because she had been drinking. Then Penny tells him that he's really smart and Leonard sarcastically replies that he's a frickin' genius (for stopping Penny). Penny wonders why all guys couldn't be like him. Leonard replies that if all guys were like him, the world wouldn't survive. Despite that, when she leaves, she kisses him again. This time, Kurt saw them and Leonard stands his ground and quickly shuts and locks the door behind him. Later, Howard asks if Sheldon has seen Raj; Sheldon answers he hasn't.
Raj is seen having just finished having sex with Cheryl (the girl from the party), despite having not said a word the entire time he's been with her. Cheryl describes Raj as a good listener.
- The costumes of the characters are:
- Sheldon is the doppler effect.
- Leonard is Frodo from The Lord of the Rings.
- Penny is a cat.
- Howard is Robin Hood (but is mistaken for Peter Pan).
- Raj is Thor, Norse God of Thunder.
- Kurt is a Jungle Hermit.
- Leonard's middle name is revealed to be Leakey, because his father once worked with archaeologist Louis Leakey. Interestingly, this show is even before Leonard's family name (Hofstadter) is first revealed.
- For once Sheldon is not detail-oriented, specifically regarding whether Raj as Thor is the Marvel Comics Avenger or original Norse God.
- Penny kisses Leonard on the lips for the first time.
- Raj has sexual intercourse for the first time (in the series).
- Howard stashed condoms in his costume.
- The favorite superhero among the guys is The Flash.
- The second choice among everyone was Frodo, which Leonard called dibs on.
- Among Penny's costumed guests are Raggedy Ann, a construction worker, a football player, a sexy nurse, a hippie, a witch, a king in over-sized novelty eye glasses (possibly Flava Flav), a rabbit, a knight, a fairy, a flapper, a cheerleader, a ladybug, a Native American Indian chief, a cave girl, a monk, and a police woman. Amy dressed up as a Raggedy Ann in the "The Holographic Excitation".
- The woman that Raj hooks up with is dressed like a ladybug.