This is how it all started. Before the opening credits, Leonard Hofstadter and Sheldon Cooper, both geniuses with respective IQ's of 173 and 187, are donating sperm in hopes that it will create "smart babies". They have second thoughts, and they leave at the right time, because when they return to their apartment, their new neighbor, the amazing beautiful Kaley Cuoco as Penny, has decided not to close her front door yet. So the guys see inside and she sees them peeking. They say their hello's and finally Leonard finds enough words to mumble out if she wants some coffee or something.
"So what do you guys do for fun around here?", a question by Penny, that led to the first of many funny comments by Sheldon throughout the series, "Well today we tried masturbating for money." And then the awesome theme song is introduced.
Penny explains the story of her life and how she has just gotten out of a relationship. She explains her destiny to be an actress and then takes a shower, while the show's other two main characters, engineer Howard Wolowitz, and Hindu, afraid-to-talk-to-women, Rajesh "Raj" Koothrapali. While she's taking a shower, we have time to see how big of nerds Howard and Raj are, too.
Leonard, in love with Penny, accepts her favor request by going to collect a TV from her ex-boyfriend, but it doesn't work out so well, as expected, and she applauds their efforts by going out to eat with them.
Bravo start to the series.