What makes a clock tick and turn; some of the world's most visited landmarks; extreme sports that surf Earth's terrain.

The River Thames; origins of machines; an ancient bartering system.

Changing a knight into a tank; the world's fastest animal; science oddities.

Diseases; sewer gators; world wonders.

The 17th century accessory that is still worn today; pop culture; the fastest way to get from country to country.

Solving everyday problems; the chances of surviving just about anything; bees.

S.O.S.; traveling in a crazy contraption; spectacular cities.

Roswell, N.M.; the history of domestic life; surprising statistics.

Flying like a superhero; a simple invention that has saved thousands of lives; the vacuum of space.

The history of the circus and cinema; the vitaphone; some pretty bad ideas.

How the brain works; the effects of caffeine; an up-close look at dinosaurs.

Famous sayings; some of history's most influential people; what life could have been without coffee; statistics about travel.

Breaking the sound barrier on land and in the air; selling the Eiffel Tower; the price of famous dentures; working out in zero gravity; the weight of bacteria in the body.

Plane crashes in Beverly Hills; airbag underwear; teen popes; wild Arizona camels; the doctor who tested catheters on himself; superhero mice.

The wrong turn that started World War I; the Titanic disaster; code cracking; a $2 million car; braving Niagara falls in a barrel; the world's biggest Ferris wheel.

The amount of neurons in the human brain; oddities in geometric figures; an extreme sport brought on by a California drought.

What a Jacob's ladder is; ways to keep pesky insects out; why fluoroscopes were a bad idea in shoe stores.

The first flying device that could carry people; doomsday prophecies; a theory involving water.

Odd acts in traveling sideshows; how long it takes to feel the effects of caffeine; the origins of Wall Street.

A high-altitude race; animals in myths and folklore; a military invention.

Why an extra month was added to the calendar; diseases that affect both humans and animals; the size of a stegosaurus brain.

This hidden-camera series follows four lifelong friends -- Brian "Q" Quinn, James "Murr" Murray, Joe Gatto and Sal Vulcano -- who take dares to an outrageous level. Since they were young, the quartet have challenged one another to do ridiculous dares in public. On the show, to find out who is best under pressure, the guys compete in awkward and outrageous hidden-camera hijinks. At the end of each episode, the loser must perform what is deemed to be the most-mortifying challenge yet.