One Direction

Why have only one Justin Bieber when you could have five?

"I like girls who eat carrots."

—Louis Tomlinson

One Direction, or 1D, is a five-piece Boy Band from Britain. They finished in third place on The X Factor, season 7. They didn't qualify for the boys section of the show, so Simon Cowell put them together and sent them into the group section, where they did well.

Members of One Direction include:

Louis Tomlinson - born December 24, 1991, hailing from Doncaster, South Yorkshire.
Liam Payne - born August 29, 1993, from Wolverhampton, West Midlands.
Harry Styles - born February 1, 1994, and hailing from Holmes Chapel, Cheshire.
Niall Horan - born September 13, 1993, born in Mullingar, County Westmeath, Ireland
Zayn Malik, born January 12, 1993 in Bradford.

They're currently^[when?] 18 (Harry, Niall and Liam), 19 (Zayn), and 20 (Louis).

One Direction provides examples of the following tropes:

All Girls Want Bad Boys: Zayn
Big Eater: Niall, definitely.
Bishonen: All of them. So pretty it is painful.
Boy Band
Cloudcuckoolander: Louis. All the time.
The Charmer: Harry. Hands down.
Embarrassing Nickname: Louis' mother apparently called him "Boo Bear" as a child. This is also used by Harry and much of the fandom.
Fake American: You wouldn't know Niall was Irish if you only ever heard him speak in his American accent. Louis pulls off a fairly good (if extraordinarily hammy) American accent, too.
Fake Brit: Niall, the same as above.
Fake Irish: While Niall is actually Irish and just good at accents, Harry (who likes to imitate Niall's accent, especially when the band is actually in Ireland) is not.
Five-Man Band

Louis - The Hero - Off-stage, by the looks of any video they post, it's Louis that runs things.
Harry - The Lancer - Because he's the most likely to go along with Louis.
Liam - The Smart Guy / Team Mom / The Heart - He's the one who looks after everyone, by his own admission, and keeps them all together off and on stage. The other boys even call him "Daddy Direction".
Zayn - The Chick - Because this troper can't justify Zayn being the Big Man.
Niall - Tagalong Kid - Not the youngest, but he was the smallest, and as Harry put it, "Niall's got immaturity down to an art form."
Simon Cowell - The Obi-Wan - Their mentor. Obvious trope is obvious.

Gasshole: Niall, according to the boys.
Getting Crap Past the Radar: The pun in the band's name, amongst other things.
Heterosexual Life Partners: There's shades of this in all of them, but the one that stands out this most is Louis and Harry. They have such an undying bromance the fans have given them a Portmanteau Couple Name: Lourry (or Larry Stylinson, depending on who you ask).
Hot Mom: According to the other boys, Harry's mom is rather foxy.
"I Want" Song: "I Want"
Keet: All of the boys have been this at one point or another -- Harry, Louis and Niall being the most prominent examples.
Large Ham: Louis, when he does anything vaguely comedic; Niall when he's imitating Peter Dickson.
Likes Older Women: Harry. Even noted by a few angry fans:

"It makes me sad to know that Harry Styles will never love me because he’s a Cake Eater and I’m only fourteen."

May-December Romance: Harry dated 32-year-old Caroline Flack, host of the Xtra Factor. Similarly, Zayn dated fellow X Factor contestant (and runner-up of their series) Rebecca Ferguson for a while. Rebecca isn't that much older than Zayn, but because Rebecca has two young children of her own, their relationship also verges into something of a Hot Mom slash Stacy's Mom territory.
Naked People Are Funny: Apparently, Harry likes to be naked. Niall's apparently been caught naked on camera too, according to Louis.
- Louis also reported (falsely) that Zayn was caught dancing naked in his apartment by his cleaner.
Name's the Same: They are being sued by a band who registered the name after their creation but before they came to the US.
Quirky Curls: Harry crosses into this sometimes.
Tall, Dark and Handsome: Zayn.
Title Track: The song "Up All Night" from their debut album is one of these.
True Companions: They were put together at the beginning of the series, and they were definitely this by the end.