Staff on the show stated a few times over the years that Penny's maiden name would never be reveled. The elevator being fixed was obvious along with and I'm guessing Penny announcing she's pregnant, with Lenard saying 'our babies will be smart and beautiful' as he did in the pilot and they happen to play that clip in the beginning of tonight's episode.
One thing I've never been able to is find an explanation for this. I originally saw The Big Bang Theory pilot a little over a month before it aired on CBS. I was working nights at the time, and when I got home from work at 2 or 3 in the morning on a night in late August 2007, I was channel surfing and I think it was Discovery Channel that I landed on and it was airing BBT. Of course I had no idea what it was, but I tuned in at the very beginning where Lenard and Sheldon were at the sperm bank, I missed the theme song, if it even had one. After watching for 5 minutes I was instantly hooked, I remember reading the synopsis for Big Bang during the upfronts and thought it sounded dumb. A few weeks later I started seeing previews for it on CBS and wondered if was what I saw that night, so I set a recording for it and sure enough it was the same thing I saw a month prior. When I saw it in August, it had no programming information in the guide and was listed as Paid Programming.
Anyone ever to bother to watch the unaired pilot?