10 Quotes That Prove Sheldon & Penny Have The Best Big Bang Theory Friendship

There are no two characters in The Big Bang Theory who are more opposite in personality than Sheldon and Penny. And yet, the theoretical particle physicist and waitress-turned-actress somehow manage to be the most dynamic on the show.

Related: 10 Quotes That Prove Leonard And Sheldon Have The Best Big Bang Theory Friendship

The combination of Sheldon's book smarts with Penny's street smarts makes for some interesting interactions, but the fact that the two characters really do care for each other makes their relationship all the more interesting to watch. Their friendship is complex, but there are a few quotes from the show that sum up their sweet connection very well.


Sheldon's Classic Knock

This is Sheldon's trademark method of knocking on people's doors, with three quick knocks in between each mention of heir name. Given that Penny lives just across the hall from Sheldon, viewers most often hear Penny's name attached to the knock.

Of course, the audience grows to love Sheldon's recurring triple-knock on Penny's door. What really makes it special, though, is that in season 10, Sheldon confides to Penny that as a child, he walked in on his father cheating on his mother. So, he does this to ensure that everyone has ample time to get their pants on. Penny is the first person that he ever tells this too, demonstrating the trust between the two.

Soft Kitty, Warm Kitty

When Sheldon spends the night in Penny's apartment and begins to feel homesick, Sheldon requests that Penny sings "Soft Kitty" to him. Penny tells him, "Soft Kitty" is only for when he is sick, to which Sheldon responds, "Homesick is a kind of sick." Of course, Penny caves.

The "Soft Kitty" song is a running theme in Sheldon and Penny's relationship. Both friends have sung it to each other when the other is feeling down. It has led to some of the most unexpectedly tender moments between the pair of pals, making this interaction a prime example that the two have a particularly tooth-rotting sweet spot for each other. Plus, relying on Penny to get him through missing his apartment with Leonard demonstrates that Sheldon and Leonard are some of TV's best roommates.

Bathroom Birthday

In the seventeenth episode of season nine, Sheldon becomes overwhelmed at his birthday party and runs to hide in the bathroom. Penny follows behind the physicist and says this sweet line to show him that she's with him no matter what.

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Penny's willingness to do whatever it takes to bring Sheldon some comfort on his birthday is the marking of a true friend. Choosing to content herself by staying with him when it all becomes too much for him to take in shows just how much she really cares for him, and Sheldon seems to really appreciate the gesture, as well.


Penny characterizes Sheldon with this brilliantly accurate Wall-E comparison while she is very high on pain medication after a fall in the shower causes her to have a dislocated shoulder.

Not only does Penny hit the nail on the head with this comment about Sheldon, but it is also a testament to how well she knows her friend. Most people might see Sheldon as unemotional and calculating, but Penny has been on the receiving end of his caring side long enough to know that he is, indeed, "full of love."

Sibling Love

At the tail-end of an experiment to see if two people can fall in love with each other over a few hours, Sheldon says this to Penny after she remarks that she sees him as a brother.

Although Penny herself quickly calls out that the latter part of the quote comes off as a bit "creepy," the sister-brother dynamic between the two friends that Sheldon agrees to feeling characterizes their closeness pretty well. It even leaves room for all of the teasing that goes on between the two that makes their friendship that much more fun.

String Theory

Penny is telling the truth when she casually says this to Leonard and Amy. Penny's musings about the nature of strings occasionally having knots sparks an idea in Sheldon that leads him to solve string theory.

Penny is not an academic as the rest of the gang is, and yet she is able to aid Sheldon in his esoteric work. This is a testament to their mutually beneficial friendship, and also that Penny is willing to sit down and really listen to Sheldon talk about the things that he is passionate about, even if she does not fully understand it at first. Plus, her ever-widening skills set is what makes her a character that fans would want to be stranded on a desert island with.

Dreaming Big

When Penny quits her job at the Cheesecake Factory to focus on her dreams of becoming an actress, she complains to Sheldon thatLeonard does not seem to understand her actions like Sheldon does, leading to one of the biggest fights between Leonard and Penny and prompting this line from the scientist.

While this quote is a bit funny coming from Sheldon, it has a sweet sentiment behind it. Despite all of their differences, Sheldon really believes that he and Penny have one thing that ties them together, and that is their ability to dream big. What makes it better is the fact that he is not at all wrong. In their respective fields, Sheldon and Penny are both shooting for the stars.

Certified Fresh

Sheldon says this about Penny while watching her perform in a play, immediately after commenting with genuine awe that "She's remarkable."

This quip is a pretty amusing jab at Penny's waitress abilities, but it only serves to emphasize just how highly Sheldon thinks of her performance. For someone who usually shows so little emotion, it is a sweet sign of friendship to hear him show such authentic admiration for Penny.


Sheldon shows up at Penny's door to thank her per Amy's request after Penny uses her entertainment industry know-how to help him with his show.

Related: 10 Jaw-Dropping Betrayals That Happened In The Big Bang Theory

For someone who does not often give compliments, this line is a very sweet and Sheldon-esque way for him to thank Penny for helping him out. Penny definitely feels the love that the quote radiates, because she tells Sheldon that he "made her day" before inviting him to come to a play that her acting class is putting on.

A Saturnalia Miracle

Penny exclaims this line when Sheldon pulls her into an embrace to thank her for the best gift that anyone could have given him: Leonard Nimoy's used and autographed napkin. After all, his love for nerdy franchises always leads to some of Sheldon's most relatable moments.

This line marks one of the most precious moments between Sheldon and Penny in The Big Bang Theory. Penny does something that means so much to Sheldon, and Sheldon does something that means just as much to Penny in return by giving her an awkward yet very sweet hug. Initiating this hug is a huge step for Sheldon, showing how he is willing to push past his limits to show Penny that he appreciates her.

NEXT: The Big Bang Theory: 10 Things To Know About Jim Parsons & Mayim Bialik's Friendship

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Gabby Etzel is a Manhattan-based writer with an affinity for the fearsome and an inexplicable identification with Throg. She’s easily charmed by two things: A well-written villain and a smoked salmon bagel.