Fake Straw Hat Crew

The Imposter Straw Hat Pirates are a group of pirates that try to look like the original Straw Hat Pirates, using the real crew's infamy under the guise of the real Straw Hats in order to gain power and more crew members. They appeared in Chapter 598.

Crewmates
The crews looks like their original counterparts but are actually humorous doubles with opposite personalities.

Brook, so far, appears to be the only Straw Hat without one of these fake Doppelgangers. This is likely due to Brook never being revealed as a Straw Hat Pirate in public, however, as the Arc is ongoing, it is possible one may be revealed before the Real Straw Hats leave Sabaody.
 * Fake Luffy: A fat middle-aged man.
 * Fake Nami: A woman with an unusually shaped head.
 * Fake Robin: A short ugly woman.
 * Fake Sogeking: A big man wearing a bogus Sogeking mask.
 * Fake Sanji: A man with messy hair.
 * Fake Zoro: A man with a beer gut and swords resembling those used by low ranking marines.
 * Fake Franky: A thin person with an unusually long neck.
 * Fake Chopper: A fox wearing a hat and a painted mustache.
 * "Wet-Hair" Caribou: A former pirate captain and brother of Coribou. Famous for killing marines.
 * "Blood-Spatterer" Coribou : A former pirate captain and brother of Caribou. Famous for killing marines.

History
They appeared on Sabaody Archipelago, they spent most of their time recruiting pirates that are over 70 million beli along with their crews. Many people took them as the real ones, due to the fact that the real Straw Hat Pirates were missing for 2 years.

They are first seen on Sabaody Archipelago in the bar where Nami was drinking, trying to recruit people for their pirate crew. They would only accept pirates who had a bounty of at least 70,000,000 beli. Their captain, the man impersonating Luffy, is a very ruthless man who does not hesitate to shoot anyone that bothers him. He shot a man trying to join the crew who had a bounty of only 55,000,000 beli, as well as a couple whom he thought was Nami and Usopp. So far, at least three pirate groups have merged with this crew, including ten men with high bounties. The two most infamous pirates to join are the brothers "Wet Hair" Caribou and "Blood-Splatterer" Coribou, infamous rookies who have bounties of 210,000,000 and 190,000,000 beli respectively.

As fake Zoro, Sanji, Robin, and Chopper were walking along the streets, an unknown group of people pursuing Robin captured fake Robin, scooping her up into a large bag.

When Chopper is first shown, he is following the fake Zoro and Sanji who then realize that its the real "Cotton-Candy Lover Chopper", they then tell fake Robin to dispose of the fake Chopper, who happens to be a fox with a mustache. They think that with the real Chopper they can attract more people to join their crew. Fake Robin is mistaken as the real one by the people who capture her, along with the fake Chopper who is biting her head. These captors then make a call stating they have arrested Nico Robin.

Trivia

 * Due to their naive personalities, both Usopp and Chopper believed them to be the real Straw Hats, even Usopp mistook Sogeking despite the fact he is Sogeking.
 * They keep misspelling Luffy's name, spelling it Monky D. Luffy on the recruitment flyers.