Like the mysterious cases that challenge Dr. Gregory House each week on Fox's hospital drama "House," things in Hollywood aren't always what they seem.

Producers at NBC Universal (which makes the show, even though it airs on Fox) opened the giant set to reporters gathered in Los Angeles for the winter press tour of the Television Critics Association. The "hospital" is enclosed in two huge buildings near a mockup of a New York City street used in other productions. Here are some things you might not know about "House":

● Golden Globe-winning star Hugh Laurie, 46, gives no hint of it on the show, but in real life the English actor has a distinctly British accent. Co-star Jesse Spencer (who plays Dr. Robert Chase) does have an accent on the show, but it's Australian (like him).

Spencer has more than just acting ties to the medical profession; his father and two brothers are doctors in Australia. His sister is in medical school.

Spencer said his brothers watch the show, often trying to guess the mystery malady of the week from the symptoms and medical jargon. They take secret pleasure in trying to find medical slip-ups in the dialogue.

● Sudoku got to be a problem on set. Omar Epps (who plays Dr. Eric Foreman) said about two months ago that the popular number puzzles were printed on scripts to give actors and crew something to do during the long days (sometimes 16 hours) when they weren't needed in a particular scene. When people started missing cues or neglecting tasks because they were absorbed in the puzzles, producers had the games removed. Still, enough people were hooked that they can be seen hiding in corners working on smuggled puzzles between scenes, Epps said.

● Laurie doesn't use a cane in real life, but on the show his character walks with a limp and depends on the cane. Limping isn't hard, Laurie said, but leaning on the cane has left him with a shoulder that regularly aches. He also argued against using his character's name as the title of the show, concerned it would make viewers focus on him instead of the ensemble. But he said he didn't have anything better to offer.

● The white board in the office where House and the other doctors write down symptoms and try to work out cases is the fourth to appear in the show. The first board was too light and moved around when House tried to write on it. A later version was clear, but the only pens that would show up on it used an ink that was hard to erase. The current version is very heavy and wipes clean easily.

● The books on the shelves of that diagnosis office are real medical texts (some titles: "When Cells Die," "Disorders of the Schizophrenic Syndrome," "Handbook of Dietary Fiber.") But they have been hollowed out to make them lighter; otherwise, moving the shelves around during set changes would take too long.

● The exterior of House's home was built on the old façade of the "NYPD Blue" headquarters.

● The MRI machine is real. It's on loan from General Electric, part of a product-placement deal (note the giant GE logo on the front).

● Sometimes, viewers will see a ceiling in a shot. That's a Hollywood mark of success. When producers have the budget to add ceilings to a set, it means the show is doing well enough to merit spending the extra money, executive producer Katie Jacobs said. Nielsen Media Research shows "House" draws about 12.5 million viewers a night. In new or shaky shows, directors just use angles that don't show the roof over actors' heads. Also, doors in the hospital have little windows that look into other hallways — another mark of success. If they can't spend the money to extend the set with blind hallways behind the window, producers use frosted glass.

● Since the hospital sets are indoors, those neighboring buildings and exterior scenes visible through the office windows are big paintings on giant plastic curtains.

● Actors being operated on slide into a wooden box, so only their head is visible. Atop the box is a silicone dummy with a chest cavity covered in hospital drapes, so the doctors can stand over the open chest and look like they're operating while viewers can see the patient's face. Demonstrating how it works, property manager Tyler Patton reached into the chest cavity and pulled out a rubber heart. Another heart, kept in a metal pan, is radio-controlled, so Patton can make it look like it's beating.

● Consultant Bobbin Bergstrom helps ensure everyone in the operating-room scenes performs duties that look medically correct. She's a registered nurse, and during breaks when new shows aren't being shot, she works shifts at Los Angeles hospitals. In some surgery scenes, it's easier for Bergstrom to don a gown and mask and act the part her-self than it would be to train an extra.

● David Foster, M.D., is a writer and story editor. He said episodes often come from his own experiences, Internet discussions and cocktail parties he attends with his doctor friends.

● The bike parked outside the lobby front door has flat tires. It's a Schwinn.

"House" airs at 8 p.m. Tuesdays on Fox.