The Cheesecake Factory

The Cheesecake Factory is a restaurant in Pasadena where Penny worked as a waitress to pay her bills, and where Leonard, Sheldon, Raj, and Howard often go to eat. Bernadette also worked here for a time before she graduated and got a job with a pharmaceutical company ("The Roommate Transmogrification").

Originally, Sheldon objected to eating, since at the time, they ate at on s. He enjoyed his  from The Cheesecake Factory so much that he changed the schedule for them to eat at the Cheesecake Factory every Tuesday. The reason for this was the Cheescake Factory cheeseburger was a single decker burger, while Big Boy produced a double decker, according to Sheldon, this gives a "much more satisfying meat-to-bun-to-condiment ratio".

During Season 2 of the show, it is revealed that the Cheesecake Factory has a bar and a performance stage. Production-wise, this set used because Kaley Cuoco (Penny) broke her leg while she was horseback riding, and the producers needed a way to hide her injury. Penny started practicing bar-tending during the first season.

Penny's job was a means to pay her bills while developing her acting career. After seeing her big break with a small role in an episode of  goes away when her scene is cut ("The Hesitation Ramification"), Penny becomes frustrated and quits in order to concentrate on acting full-time ("The Occupation Recalibration"). The last time the set is seen is when Penny is in front of the bar talking to Leonard when she returns her uniform.

There is an down the street.

Significance in the series
The Cheesecake Factory is the primary source of Penny's income in the series. She works there as a waitress and bartender, and always serves the guys when they come in (albeit season 2). Bernadette also worked there as a waitress before getting her PhD.

The Cheesecake Factory serves free cheesecake slices on someone's birthday when they come in. It is against restaurant policy to give out free nachos.

Penny meets her on-and-off boyfriend Zack Johnson here, who works for a family run company that designed the menus for The Cheesecake Factory.

In addition, The Cheesecake Factory has a walk-in freezer in back, as seen in The Monopolar Expedition, where Leonard, Sheldon, Raj, and Howard simulated Arctic conditions to train for their 3 month expedition to the magnetic north pole.

Sheldon always orders the barbecue bacon cheeseburger with the barbecue, bacon and cheese on the side.

Leonard cannot have any "cheese" products, being lactose intolerant.

Background
The Cheesecake Factory as depicted on the show bears little, if any, resemblance to the actual chain of restaurants (including the sole Cheesecake Factory in Pasadena, California) which typically have a more upscale decor than the restaurant depicted on the show. The restaurants are usually decorated in neutrals and reds with decor including elements such as (faux) stone columns. Restaurants do not typically have a stage or musical performances in them.

The uniforms depicted on the show also have no connection to the uniforms worn by actual Cheesecake Factory staff.

Trivia

 * Sheldon always orders the barbecue bacon cheeseburger with the barbecue, bacon and cheese on the side.
 * The Cheesecake Factory also produces: sea bass, meat-lovers pizza (can be served without meat), Shepherd's pie, Caesar salad, nachos, quesadilla (can be served with soy cheese), iced tea (and alcoholic beverages served either at the table or at the bar), water, chicken tortilla soup, potato leek soup, chocolate key lime pie, carrot cake and various other desserts.
 * The Cheesecake Factory has two pages of desserts on their menu.
 * The Cheesecake Factory have 'specials' which change on a daily basis.
 * The performance stage has been used thrice, once by Howard on his own, the other time accompanied by Amy. The third time Sheldon was singing and playing Keyboard, because Penny secretly mixed alcohol in his drinks thus he became inebriated.
 * The Cheesecake Factory provides free birthday cheesecakes.
 * Staff who are tending bar do not wear the same uniform as the waitresses.