Season 4

Season 4 of The Big Bang Theory returned to television on September 23, 2010, and contained 24 episodes. Throughout the season, both Sheldon and Howard become more involved in their girls/girlfriends and Penny realizes her true feelings for Leonard following their third season break-up, especially after Leonard begins to date Raj's younger sister, Priya. While Amy and Bernadette were main characters in season 4, some episodes have them with minimal screen time.
==Cast==
=== Main Cast ===
*Johnny Galecki as Leonard Hofstadter (24/24)
*Jim Parsons as Sheldon Cooper (24/24)
*Kaley Cuoco as Penny (22/24)
*Simon Helberg as Howard Wolowitz (24/24)
*Kunal Nayyar as Rajesh Koothrappali (24/24)
*Mayim Bialik as Amy Farrah Fowler (15/24)
*Melissa Rauch as Bernadette Rostenkowski (15/24)
=== Recurring Cast ===
* Carol Ann Susi as Debbie Wolowitz (7/24)
* Kevin Sussman as Stuart Bloom (3/24)
* Aarti Mann as Priya Koothrappali (10/24)
* Brian Thomas Smith as Zack Johnson (3/24)
* Brian George as V. M. Koothrappali (2/24)
* Alice Amter as Mrs. Koothrappali (2/24)
* Ian Scott Rudolph as Captain Sweatpants (2/24)
* Owen Thayer as Lonely Larry (2/24)
=== Guest Cast ===
* Vernee Watson as Althea Davis
* Laurie Metcalf as Mary Cooper
* Wil Wheaton as Himself
* Joshua Malina as President Siebert
* John Ross Bowie as Barry Kripke
* Charlotte Newhouse as Joy
* Annie O'Donnell as Mrs. Fowler
* Eliza Dushku as Angela Page
* Keith Carradine as Wyatt Teller
* Rick Fox as Glenn
* Jessica Walter as Mrs. Latham
* Christopher Douglas Reed as Todd Zarnecki
* Lanny Joon as Officer Shin
* Arnold Jun as Ho-Jun
* Eric Andre as Joey
* Tiffany Dupont as Angela
* Whitney Avalon as Elsie
* Phil Abrams as Dr. Bernstein
* Steve Wozniak as Himself
* Katee Sackhoff as Herself
* George Takei as Himself
* Neil deGrasse Tyson as Himself
* LeVar Burton as Himself
* Brian Greene as Himself
==Episodes==
Episode (Series)	Episode (Season/Ep#)	Title 	Original Air Date 	Directed By 	Description
64 	401 	The Robotic Manipulation 	September 23, 2010	Mark Cendrowski	Howard demonstrates a robotic arm, that he "borrowed" from the Jet Propulsion Laboratory.  To everyone's surprise, Sheldon announces his plans to conceive a progeny with Amy via in vitro fertilization. Penny comes to know of Sheldon's new friend and asks him to take Amy on a date which she ends up chaperoning.
65 	402 	The Cruciferous Vegetable Amplification	September 30, 2010	Mark Cendrowski	Sheldon determines that his best estimate for his life expectancy by changing his diet and then building a robot to take his place.
66 	403 	The Zazzy Substitution 	October 7, 2010 	Mark Cendrowski	Sheldon and Amy Farrah Fowler are very compatible with each other. They break up over whose profession is more important which causes Sheldon to start collecting cats.
67 	404 	The Hot Troll Deviation 	October 14, 2010 	Mark Cendrowski	When the guys run into Howard's ex at the Cheesecake Factory, he ends up confronting his lingering feelings for her. He seeks help from Penny, who agrees on the condition that Howard reveal the reason behind his breakup.
68 	405 	The Desperation Emanation 	October 21, 2010 	Mark Cendrowski	When Amy Farrah Fowler decides to introduce Sheldon to her mother, it worries Sheldon. He decides to end their platonic friendship.
69 	406 	The Irish Pub Formulation 	October 28, 2010 	Mark Cendrowski	Raj's sister Priya visits and inadvertently causes trouble for the friends. She and Leonard apparently have a history, despite Leonard's pinky swear with Howard that they would not interact with her in deference to Raj. They hook up, but are discovered by Sheldon, who devises an overly elaborate lie to cover it up.
70 	407 	The Apology Insufficiency 	November 4, 2010 	Mark Cendrowski	When Howard attempts to receive a high security clearance, his friends are interviewed by a formidable FBI agent checking into Howard's past. Raj and Leonard are pathetic during their respective interviews, while Sheldon reveals too much.
71 	408 	The 21-Second Excitation 	November 11, 2010 	Mark Cendrowski	Sheldon, Leonard, Raj, and Howard excitedly plan to attend a screening of Raiders of the Lost Ark that includes 21 seconds of never-before-seen footage. However, they delay reaching the theater, resulting in much complaining from Sheldon, which becomes worse when Wil Wheaton arrives. Amy starts to bond with Penny during a sleep over.
72 	409 	The Boyfriend Complexity 	November 18, 2010 	Mark Cendrowski	Leonard is flattered when he shows up at Penny's door and gets a kiss from Penny. Later, Penny informs him that her critical father Wyatt is visiting, and she asks him to pretend that they're back together because he's the only boyfriend she's ever had that her father likes.
73 	410 	The Alien Parasite Hypothesis 	December 9, 2010 	Mark Cendrowski	Amy begins to have feelings for Penny's ex Zack, whom she meets in a bar on a night out with Penny. After she and Sheldon decide that Amy is horny, Sheldon sets her up on a date with Zack.
74 	411 	The Justice League Recombination 	December 16, 2010 	Mark Cendrowski	The guys discover that Penny and her ex-boyfriend, Zack, are back together. Much to Penny's annoyance, she and Zack end up going to the comic book store New Year's Eve party as Wonder Woman and Superman.
75 	412 	The Bus Pants Utilization 	January 6, 2011 	Mark Cendrowski	Sheldon, Howard, and Raj are eating together in the Cafeteria when Leonard approaches them with an idea for a smartphone app that helps users solve Differential Equations. Leonard quickly recruits Howard, Raj, and reluctantly Sheldon who becomes too obnoxious and gets bumped from the team.
76 	413 	The Love Car Displacement 	January 20, 2011 	Anthony Rich 	Leonard, Sheldon, Howard, Raj, Amy, and Bernadette are invited to be on a discussion panel at  a symposium in San Francisco. Amy invites Penny as her guest which results in multiple hotel room bed hopping.
77 	414 	The Thespian Catalyst 	February 3, 2011 	Mark Cendrowski	Sheldon gives a lecture in a class and receives mulitple negative comments. To help him, Amy suggests that he take acting lessons from Penny.
78 	415 	The Benefactor Factor 	February 10, 2011 	Mark Cendrowski	President Siebert makes the gang attend a fundraiser for the university. One of the attendees invites Leonard to dinner.
79 	416 	The Cohabitation Formulation 	February 17, 2011 	Mark Cendrowski	Bernadette asks Howard to consider living together. Howard fights with his mother and moves out. Leonard and Priya start their relationship.
80 	417 	The Toast Derivation 	February 24, 2011 	Mark Cendrowski	Sheldon is upset when he realizes Leonard is the center of their group of friends. When the gang starts hanging out at Raj's, Sheldon decides, on advice of Amy and Penny, to get a new group of friends, which consists of Kripke, Stuart, Zack, and LeVar Burton.
81 	418 	The Prestidigitation Approximation 	March 10, 2011 	Mark Cendrowski	Priya talks Leonard into getting contact lenses. Howard and Raj perform a magic trick that Sheldon becomes obsessed with figuring out. 
82 	419 	The Zarnecki Incursion 	March 31, 2011 	Peter Chakos 	Sheldon's World of Warcraft account was hacked and his character was raided clean, the boys are determined to track down this hacker. Penny helps them deal with the thief.
83 	420 	The Herb Garden Germination 	April 7, 2011 	Mark Cendrowski	Amy and Sheldon use the members of their social group for an experiment on the spread of gossip.
84 	421 	The Agreement Dissection 	April 28, 2011 	Mark Cendrowski	After Sheldon barges into the bathroom and finds Leonard and Priya in the shower together in violation of the Roommate Agreement, Priya as a lawyer reviews it and finds loop holes in the document.
85 	422 	The Wildebeest Implementation 	May 5, 2011 	Mark Cendrowski	Penny and Amy use Bernadette, codename Wildebeest, to spy on Leonard and Priya at a dinner party she and Howard are attending.
86 	423 	The Engagement Reaction 	May 12, 2011 	Howard Murray 	Bernadette has lunch with Howard's mother who ends up in the emergency room immediately after learning of their engagement. Penny and Priya start bonding over Leonard's quirks.
87 	424 	The Roommate Transmogrification 	May 19, 2011 	Mark Cendrowski	Leonard and Priya decide to live together in Raj's apartment, while Raj can become Sheldon's roommate. Sheldon is very happy after Raj prepares dinner for them. Penny and Raj get drunk together and have a one-night stand. 
==Gallery==
Big-bang-theory-barbarella-i12760.jpg|Season 4 Poster
Penny (Season 4 Promo).jpg|Penny.
Penny (Season 4 Promo Photoshoot).jpg|Penny.
Penny and Leonard (Season 4 Promo Photoshoot).jpg|Penny and Leonard.
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 Season 04
Category:Howard-Bernadette
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Category:Seasons
 
Category:Marriage Proposal
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Category:Sheldon has a date
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de:Staffel 4
es:Cuarta temporada
it:Quarta stagione
pt-br:4ª temporada