Plot

Penny is furious with Leonard and Sheldon when they sneak into her apartment and clean it while she is sleeping.

Penny asks a favor of Leonard and Sheldon: to let the furniture delivery men into her apartment when they make the delivery of her recent purchase. She gives them a key to her apartment for this task. Leonard and Sheldon regret agreeing to do so when first the delivery men will not carry the delivery up the four flights of stairs, and second when they see the pigsty that is Penny's apartment, which just does not sit right with Sheldon's orderly attitude. Penny also ends up regretting asking them when Sheldon uses the key to sneak into her apartment at night when she is sleeping to tidy up, a task in which Leonard participates. Can Penny ever forgive them for violating her personal space, regardless of how immaculate the apartment looks?—Huggo

When Penny asks Leonard and Sheldon to accept a package for her while she's at work, Sheldon is shocked when he gets a look at her unkempt apartment. That night, he sneaks into her apartment and when she wakes up, she's furious when both of them and demands her key back.—Jerry Roberts

Penny asks Leonard and Sheldon for a simple favor: receiving a package of furniture while she is at work, but when Sheldon discovers the chaos in her apartment he sneaks in her apartment at night and cleans it while she is sleeping and Leonard joins him. When she wakes up she is very upset, but the guys still end up helping her with her house.—Naw Neine

Penny bought a new furniture and asks Leonard if he can receive the delivery for her. He agrees and she gives a copy of her apartment key to him. Leonard and Sheldon find that her apartment is a complete mess. During the night, Sheldon's Obsessive Compulsive Disorder (OCD) affects his sleep and sneaks into Penny's apartment to clean and straighten. Leonard misses Sheldon and ends helping him in his task. When Penny discovers that they went to her apartment while she was sleeping, she becomes mad at them.—Claudio Carvalho, Rio de Janeiro, Brazil

Penny has to work during the day and requests Leonard to take a delivery of an IKEA furniture, which she had ordered) on her behalf. She gives her keys to her apartment for the same. The guys argue about whether Superman has ability to fly or is it a feat of strength. Sheldon postulates that it is a feat of strength similar to leaping tall buildings. He has energy storing Kryptonian skin cells that help him fly at night. When Sheldon and Leonard carry a box of flat pack furniture (3 flights of stairs & reasonably heavy) that came for Penny (Sheldon is sure that this favor for Penny wont increase Leonard's chances of having sex with her), Sheldon is deeply disturbed at how messy and disorganized her apartment is.

Later that night, while Penny sleeps, the obsessive-compulsive Sheldon, unable to sleep, sneaks into her apartment to organize and clean it. Leonard finds out and reluctantly helps him. Sheldon asks Leonard to speak in a lower register as evolution has made women more sensitive to higher registers so that they can hear their crying babies.

The next morning, Penny is furious to discover that the guys had been in her apartment while she was asleep in her bedroom. Sheldon tries to apologize to Penny but fails by remarking that Leonard is a "gentle and thorough lover". He also wants to know if Penny objects to the guys breaking in at night, while she was sleeping, or does she also object to the new organizational paradigm. Penny is speechless and shuts the door on Sheldon, after taking her keys back from Leonard. Later, Penny encounters Raj in the hallway. Though he cannot talk to Penny, she calms down whilst telling him about the issue (Raj just continues to listen to Penny, and she mistakes that for his good listening abilities), reasoning the guys were just trying to help her, and then hugs Raj.

Then Leonard apologizes to Penny, prompting Penny to forgive and hug him. Later the guys assemble Penny's entertainment center after totally ignoring Ikea's instructions. They decide that the Swedish designs are inefficient (which is why Sweden does not have a space program). The decide to use the empty space behind the flat screen TV to install a sound system. They also decide to install a liquid heat exchanging device, built from using aluminum pipes and other industrial grade materials. The guys disperse to arrange the materials and an acetylene torch and gather at Penny's apartment in an hour. In the meanwhile Penny finds the instructions self explanatory and goes about building the furniture all on her own.

Title reference: Sheldon having Big Bran cereal (with higher fiber content) after Penny finds out her apartment has been rearranged. Sheldon arranges all the cereal in the apartment sorted by their fiber content. At first he wanted to celebrate the cleaning of Penny's apartment by going for a low fiber choice, but quickly changed to Big Bran once he understood how upset Penny really was with the sequence of events that transpired the previous night.