1. metals
   gases
2. gemstones

All three of this items are gemstones, created over millions of years from minerals within the Earth. Because they take so long to form and are relatively scarce, they are often sold at high prices, though laboratory scientists are working hard to make ultra-realistic synthetics at a fraction of the cost.

1. salads
   empires
2. British colonies

All three of these are empires that once controlled large portions of the world. The Roman empire lasted from around 27 B.C. to 476 A.D., while the Greek empire was earlier, lasting from 800 B.C. to 146 A.D. The Byzantines flourished between 330 and 1453 A.D.

1. boroughs
   states
2. cities

New York City is one of the most densly-populated cities on the planet. While many people picture Manhattan when they think about NYC, the city itself actually consists of five separate areas, known as boroughs. These five include Manhattan, of course, along with Brooklyn, Queens, the Bronx and Staten Island.

1. Twilight characters
   Harry Potter characters
2. Star Wars characters

J.K. Rowling became a household name when she released the first book in her Harry Potter series in the '90s. For the next decade, fans flocked to bookstores and movie theaters to follow the adventures of boy wizard Harry Potter and his friends Ron and Hermione.

1. Dickens characters
   Stephen King characters
2. Shakespeare characters

Hamlet, Macbeth and Othello are all characters taken from plays by William Shakespeare which were written in the early 1600s. Shakespeare ranks among the greatest writers of all time; he penned 39 plays and over 150 sonnets.

1. Disney rides
   Cedar Point rides
2. Six Flags rides

All of these iconic roller coasters can be found at the Magic Kingdom at Walt Disney World in Florida -- Space Mountain in Tomorrowland, Thunder Mountain in Frontierland and Seven Dwarfs Mine Train in Fantasyland.

1. '00s TV shows
   Stephen King books
2. songs by The Rolling Stones

All three of these are classic horror novels by master of the macabre Stephen King. Published in 1974, "Carrie" was King's first novel. "It" cane out of the sewers in 1986, followed by "Misery" in 1987.

1. drinks
   cheese
2. haircuts

All three of these are types of cheese. Gouda is named for the town of Gouda in the Netherlands, while Swiss cheese originated in Switzerland and is known for its holes. Cheddar comes from a town called Cheddar in Somerset, England, which has a series of caves perfect for aging cheese.

1. baseball stats
   football stats
2. health stats

All three of these are stats used to evaluate the performance of baseball players. RBI stands for runs batted in, OBP for on-base percentage and ERA for earned run average.

1. famous TV dogs
   candy bars
2. cartoon characters

All three of these are characters from the "Looney Tunes" movies and cartoons. Believe it or not, Porky Pig is the oldest, starring in films as early as 1935. Daffy Duck came next, in 1937, and Bugs Bunny was last, in 1940.

1. rivers
   languages
2. animals

The Yangtze, Yellow and Mekong are all rivers located in China. At approximately 3,900, 3,400 and 2,700 miles, respectively, they also rank among the top ten longest rivers in the world.

1. colors in rainbow spectrum
   colors in American flag
2. colors in Mexican flag

Red, white and blue are the colors of the American flag. The red and white stripes represent the original 13 colonies, while the white stars against a blue background represent the 50 states that make up the union.

1. Star Trek ships
   Christopher Columbus' ships
2. Star Wars vessels

For his maiden voyage to the "New World," Columbus left Portugal on August 3, 1492 with three ships -- the Nina, the Pinta and the Santa Maria. All three were slow and sturdy. The Santa Maria ran into land on the island of Hispaniola and ended up being abandoned by Columbus and his crew.

1. Madonna albums
   Beatles albums
2. John Denver albums

Madonna became a huge star when she released her first album, "Madonna," in 1983. She gained even more fans as she continued to produce albums, including "True Blue" in 1986, "Like a Prayer" in 1989 and "Ray of Light" in 1998.

1. Powerpuff Girls
   My Little Ponies
2. Disney Princesses

Blossom, Bubbles and Buttercup are the three main characters of '90s and '00s cartoon show "The Powerpuff Girls." They live with their father, Professor Utonium, and help protect Townsville and the world from Mojo Jojo and other villains.

1. The Three Amigos
   The Three Musketeers
2. The Three Little Pigs

Alexandre Dumas penned his classic "The Three Musketeers" in 1884. Set in the 1620s, it tells the story of d'Artagnan and his adventure to meet Porthos, Aramis and Athos.

1. birds
   car parts
2. chess pieces

All three of these are chess pieces. Each player in a game gets the same 16 pieces in either white or black, and the game takes place on a 64-square board.

1. kids on "Married with Children"
   kids on "The Simpsons"
2. kids on "Family Guy"

Bart, Lisa and Maggie are the three children of Homer and Marge on "The Simpsons." Though the show premiered in 1989, none of the kids have aged.

1. cities in Germany
   cities in Russia
2. cities in France

All three of these are cities in France. Paris is the capital and home to the Eiffel Tower. Normandy is famous for being the site of the D-Day invasion in WWII, and Lyon is located in the eastern part of the country, near the Swiss border.

1. dog breeds
   cat breeds
2. birds

All three of these are breeds of dogs. Rottweilers are known for their sturdy strength, pugs for their wrinkled faces and poodles for their clipped curly coats.

1. beverages
   trees
2. flowers

Fir, pine, spruce, hemlock and yew are all type of softwood trees, but don't let the name fool you. Softwood simply means that the trees are conifers, rather than broad-leafed plants like oaks or elms.

1. federal holidays
   President's birthdays
2. dates of total eclipses

All three of these are federal holidays in the United States that fall on the same date each year -- Christmas on December 25, New Year's Day on January 1 and Independence Day on July 4.

1. dogs
   birds
2. cats

These are all breeds of cats. Siamese cats are known for their tan coats and blue eyes, while Persians have long luscious locks. Bengals are a slightly less common breed, with spots that make them resemble jungle cats.

1. Fords
   Toyotas
2. Chevys

The Camaro, Cavalier and Corvette are all car models produced by Chevy. The Corvette came out in '53, the Camaro in '66 and the Cavalier in '82.

1. Bush children
   Kennedy children
2. 21st-century British royals

John, Robert and Rosemary were three of the children of Joseph P. Kennedy Sr. and his wife Rose, who had nine kids altogether. John became President in 1961, Robert was assassinated on the campaign trail in 1968, and Rosemary was subject to a lobotomy at the age of 23 and spent her life in an institution.

1. insects
   birds
2. cats

All three of these are types of birds. The tiny sparrow eats seeds and insects, while the raven is known for its shiny black feathers. The pigeon thrives in urban environments where many other birds would struggle for resources.

1. Star Trek ships
   NASA shuttles
2. Star Wars ships

All three of these are vessels seen in the Star Wars universe. The TIE fighter is a compact Imperial starship, while the Star Destroyer is a larger wedge-shaped vessel used by the Imperial Navy and Galactic Republic. Han Solo himself piloted the trust Millennium Falcon in "A New Hope."

1. Star Trek captains
   Harry Potter characters
2. Star Wars characters

Kirk, Picard and Sisko all captained the Star Trek Enterprise at one point in the history of the series. Kirk was the first on the original '60s series. Ben Sisko served as Captain on "Deep Space Nine," while Jean-Luc Picard took on the role in "The Next Generation."

1. plants
   fruit
2. Harry Potter dragons

All three of these are names of common plants. Each is generally grown indoors, known for its easy care, and often used to improve air quality within the home or office.

1. famous dogs
   bands
2. stars

These are all the names of well-known stars in the sky. You may know Polaris as the North Star, or Sirius as the Dog Star. Vega has a bright blue glowand is part of the Lyra constellation.