Big Bang Theoryran on CBS for 12 reasons . The situation comedy pore around the lives of five persona , Sheldon , Leonard , Raj , Howard , and Penny , with two additional main character added in the later seasons , Bernadette and Amy , along with several other support eccentric and invitee appearance .

Despite the intricate geek - speak on the show , since the admirer were all skill nerd work in physics , applied science , neuroscience , and other interchangeable orbit at Caltech University , fan loved the show , making it one of the most popular on television .

One elision was Penny , who was a waitress and aspiring actress turn pharmaceutic sales representative who was n’t into Star Trek , Star Wars , and scientific discipline like the others . But she was central to the story nonetheless . Yet strangely , Penny never had a last name . Why was that ?

Anna Silk as Bo from the TV show Lost Girl

Many theories have floated around the cyberspace , especially since , even in the final episode , her surname was never revealed . Here ’s a look at 5 of the most unconscionable theories , and 5 Sojourner Truth about why we never found out .

Penny Was A Spy: Theory

One of the most freaky theories suggest that Penny was really a spy , sent to keep an oculus on Sheldon and Leonard . It could make mother wit , given that they were both working on pretty important inquiry that might interest the politics . Indeed , at one head , they did find themselves recruited by the authorities for a project .

Some theorists even go so far as to say that this is whyPenny steals their Internet . It is n’t because she ca n’t afford her own , but because it makes it easier for her to spy on them . This is just way too far - fetched for a sitcom , though .

It Wasn’t Intentional: Truth

The show had aired a number of episodes already , during which time we learn of the surnames of all other major fictitious character , include Sheldon ( Cooper ) , Leonard ( Hofstadter ) , Raj ( Koothrappali ) , and Howard ( Wolowitz ) . Yet we had no idea what Penny ’s last name was . In fact , on the IMDb page for the series , it simply shows “ cent ” as though she was a minor character , even though she ’s list third on the charge .

Even Bernadette ( Rostenkowski ) and Amy ( Farrah Fowler ) , who joined the cast afterwards in the series , have surnames , as do support characters like Stuart ( Bloom ) and Bert ( Kibbler ) . But the the true is that it was n’t designed to allow for out a surname for Penny . It just sort of happened .

Penny Was a Stage Name: Theory

Penny did move to California with hopes of becoming an actress . So one hypothesis intimate that not only do we not hump her surname , but Penny was n’t even her real first name . Rather , it was a phase name she borrow so as to get more acting jobs .

It would stand to grounds , then , that if Penny was n’t even her birth name , why would we even need to bed her last name ? If anything , we ’d want to know her veridical given name . Of course , there ’s no truth to this flaky theory .

Producers Got Superstitious: Truth

After the show had been draw for a while , producer see they had never mentioned Penny ’s last name . It was n’t intentional , it just was never discussed and never terminate up being pen anywhere into the script . And after that , they became superstitious about revealing it .

“ We got anxious and superstitious and give her [ a last name ] , ” confirmed executive manufacturer Steve Molaro at the Wondercon panel this past March . It really is as childlike as that , though slenderly troubling that there was reason to bring out the cognomen of the other characters . It could also be that they worked in a formal educational system were many colleagues advert to them as Mr. Cooper or Mr. Wolowitz , whereas Penny , in the beginning , was a waitress who was only ever referred to by others using her first name .

It’s Johnson: Theory

Some fans in on-line forums blaspheme that her last name was Johnson because it was revealed at one spot thatshe married Zack Johnson in Las Vegas , not consider that it was existent . If this was the case , then legally , her name would be Johnson , veracious ?

Well , not really . Even if she did tie him , unless she actually filled out prescribed name alteration documents , her last name would have remained the same . That said , others note that Johnson is the most usual surname in Nebraska , where she ’s from . So it ’s entirely potential that Johnson was her last name anyway , before she even conjoin Zack . But probably not .

It’s Hofstadter: Truth

OK , so we technically do n’t know if Penny ever had her surname legally change to Hofstadter after splice Leonard , which is n’t a necessity . These are the types of mundane details that are n’t necessary to show in a situation comedy . Though it would have present a swell opportunity to bring out her maiden name .

however , at the Wondercon venire in March , executive manufacturer Steve Molaro confirmed that Penny ’s last name “ will always be Hofstadter . ” Some have criticized this whimsy , saying it implies that Penny did n’t have an identity until marrying Leonard . But the truth is that she was Penny , and that ’s her individuality . She does n’t postulate a last name to sustain it .

It’s Longbottom: Theory

In addition to supposition about Johnston , some others account believe that the name was Longbottom . Yet there ’s no denotation to prove this and it seems to be nothing more than cyberspace lore .

The hypothesis is that this name was bespeak on episode transcript , which someone , somehow got wind of and “ leak out ” the details . But again , this has n’t been substantiated , so really , it could have been anything written on those former transcripts . Only a select few people actually know the verity .

Kaley Cuoco Doesn’t Want to Reveal It: Truth

Kaley Cuoco , the histrion who play Penny for all 12 seasons , say she does n’t really want to ever discover what Penny ’s last name was . “ It ’s kind of a personal matter , ” she told CBS News in 2017 . “ It feels like a jinx . We have n’t say it for so long . I experience like if we say it , the earthly concern would explode . ”

This implies that Cuoco knows what Penny ’s last name is supposed to be , presumptively having see it in the original script . Either way , it sounds like fans will never recover out .

She Doesn’t Have A Last Name: Theory

Like Cher or Madonna , some advise that Penny simply does n’t have a last name . Of naturally both Cher and Madonna , and every other one - discover creative person , really have surnames . So this is one of the sillier of the many theories .

And in actuality , this “ hypothesis ” was first presented by Kaley Cuoco herself , meant to be in jape . This was her response one time when asked about the mysterious missing name . The truth is that Penny did have a last name , as anyone would .

Kaley Cuoco Was More Concerned About the Elevator: Truth

While Kaley Cuoco , who plays cent , seemed hunky-dory with the character ’s surname never being revealed , as she note in interviews prior to the net sequence airing , there was one thing she did desire to get resolved before the series came to a conclusion : that shucks elevator that was always   out of service in the construction .

She dumbfound her indirect request , asin the last episode , the lift was finally set , much to the shock and awe of Sheldon , who rode in it with cent for what seemed like the first time . The running joke throughout the series is that the lift was always out of service , go forth the gang to footslog up several flights of stair to their apartment . The clip they spend walking , however , was when many authoritative conversation took lieu .

A closeup of Nathan Fillion as John Nolan from the Rookie season 7

Star Wars Stormtrooper

Penny looking up at the camera on TBBT

Penny looking angry at someone off camera in Big Bang Theory

Penny crying on the wall in The Big Bang Theory

Penny talking to Leonard.

Penny on the couch smiling in TBBT

Big Bang Theory Penny Zack drinking wine

The Big Bang Theory Penny and Leonard

Penny in Sheldon’s spot in The Big Bang Theory

Penny looking worried in TBBT

Penny looking annoyed in The Big Bang Theory.

The Big Bang Theory elevator