As a thank you to director Josh Whedon (who helped back their kickstarter project,
"The Letter Carrier"), actors Jesse L. Martin, Carlos Valdes, And Rick Cosnett Sing The 'Firefly' Theme Song (
link).
Just an amazing acapella tribute, and boy, these guys can sing!! Their Kickstarter short is going to have more of this style, and I can't wait for them to finish!