She asked favors of him and talked and visited him nearly every day. He took Penny out for dinner in "The Fuzzy Boots Corollary"; however, Penny thought the whole gang was coming.

When no one else showed up she suspected their evening was supposed to be a date.

Leonard: Well, why don't we just figure out where we're going, and when we want to get there, and then rate of speed equals distance over time, solve for 'r'.

Season four started four months after the end of season 3. Johnny Galecki submitted the episode "The Benefactor Factor" for consideration due to his nomination for the Primetime Emmy Award for Outstanding Lead Actor in a Comedy Series at the 63rd Primetime Emmy Awards.

The panel opened with a funny taped message literally explaining the big bang theory by reading the show's theme song and a highlight reel from the series' nerdiest moments and included a pretaped message from guest star Stephen Hawking explaining the theory by "singing" the show's theme song.

The writers shared the inside stories behind some of the show's most iconic moments.

Penny: Look, just forget I told you about me not graduating from community college, okay?

I haven't forgotten a thing since the day my mother stopped breast-feeding me. Penny: I meant has he ever been involved with someone who wasn't a brainiac? Well, a few years ago, he did go out with a woman who had a Ph.

During the season, actress Kaley Cuoco was absent from two episodes after she fell off a horse and the horse accidentally crushed her leg.

When she returned to the series, she was shown working as a bartender instead of waitressing at her usual workplace, The Cheesecake Factory, to hide her injury.

"It's not as exciting as a wedding night." PHOTOS: ' The Big Bang Theory's' Nerdiest Guest Stars "We work around the clock to bring you science facts," Holland said, jokingly adding that spiders grow rubies on their underbellies.