In the series, Browncoats were named after the simple brown dusters the soldiers of the Independence faction in the show had worn as uniforms. Conversely, the Alliance's soldiers were called "Purplebellies," because of the purple-tinted body armor they wore on their chests.
In 2002, while Firefly was nearing cancellation, fans organized to try to save the series from being canceled by Fox Broadcasting Network. Their efforts included raising money for an ad in Variety magazine and a postcard writing campaign to UPN. These fans are also sometimes known as "flans" (IPA /flænz/). This originated from a slip of the tongue by actor Nathan Fillion during an interview, when talking about Firefly fans. (Wikiquote transcription)
Since then, there have been several Browncoat fan films. One titled Browncoats: Redemption raised $113,000 for charity. The film centered around the crew of the ship Redemption, three months after the Miranda signal is sent.
A number of fan groups and charitable organizations were created by browncoats across the globe. Notable charitable groups include Austin Browncoats, California Browncoats and Southeastern Browncoats.
Can't Stop the Serenity is a global charitable event to benefit Equality Now and other causes (chosen at the local level, some cities include Kids Need to Read, a charity co-founded by Firefly/Serenity star Nathan Fillion and author PJ Haarsma). The project began in 2006 and has raised a combined total of more than $600,000.
^McGILL, HANNAH (Oct 6, 2005). "Hungry for the real Roman Cinema FILM OF THE WEEK". The Herald (Glasgow, Scotland). p. 8. [Reviewing the film Serenity]... [t]he intricacies of the plot, however, are really of interest only to browncoats (yes, there are enough Firefly obsessives that they have their own special name)