Bernadette would undoubtedly know because she is a cow orker at The Cheesecake Factory and would see the name on a work schedule.
I didn’t even know her last name was a secret. I thought we’d heard it before, but I guess not.
… I also never noticed that we were not expected to know Penny’s last name, as the omission has never been an issue.
They covered that very well–Leonard called him “Sir” a couple of times, and he said “Son, you can call me Wyatt”
Trivia:The first mention of Penny’s father was in The Maternal Capacitance, where she called him ‘Bob’. However, his name was later changed to Wyatt.
I’m hoping her last name is either a brand of liquor, or “Banger”
Sfrumeven
Faryerthawts
If she had family connections in the entertainment industry, wouldn’t her acting career have taken off by now?
Titfuck.
You heard it here first.
Edit:
Count me in as someone that didn’t know this was a thing as well.
Here is the relevant passage in the OP’s linked article:
This rather succinct reply, buried among a number of much more interesting (IMO) Q’s and A’s, leads me to believe it’s not necessarily a big secret or will necessarily be a big important reveal. So I voted “mundane.”
Voting for this one.
While I agree with the essence of this. If the name is mundane enough, like let us say, Newton, it can be both geeky and common and opening up potential plot lines like she is a direct descendent of Sir Issac. Even Teller I suppose is a possibility, but Openheimer, Einstein and Galileo are probably out.
Wise?
Yeah, they had to have known it. They are always meeting at the mailboxes and Leonard even got her mail at one point. So I never considered it a plot-point.
Nah. If it was, then “Lois Lane” and “Margo Lane” comments would be flying nonstop.
I don’t think it could reasonably be made into a plot point - it’s just something that sad little people like us like to speculate about on the internet, and the cast and production team therefore have to field questions about it from time to time.
New favourite: “Penny London,” from this little bit of anecdata dropped by Jim Parsons:
It can’t be Newton. They surely would have mentioned it in the episode where Sheldon was teaching Penny about Physics and the discussion turned to fig cookies.
As for Penny Lane, I don’t think the guys would even get that reference. That could be why Penny likes them, they’re the first people she’s ever hung out with that didn’t tease her about her name.
Candy.
Ante.
Playing off of her father’s first name-Earp.
Really? I don’t think that even Sheldon seems insulated enough from popular culture for that one to pass without comment. 
Coyne.
Leonard and Sheldon didn’t know who Tweety Bird was.
TWEETY BIRD.
There is nothing they’re not too sheltered to not know.