When Joss Whedon himself donates to your Kickstarter, there’s apparently only one proper way to thank the man who’s given birth to some of pop culture’s most beloved TV series and films: with a song.

That’s exactly what a trio of The Flash actors did after The Avengers: Age of Ultron directed donated to The Letter Carrier, a short film Kickstarter project. The Flash‘s Jesse L. Martin, Carlos Valdes, and Rick Cosnett, who all have various roles on the project, thanked Whedon by singing the theme song to his short-lived but beloved television series Firefly.

Martin wrote the script and original songs for the project, composed the music alongside Valdes, and will direct and produce the film with Cosnett.

Watch the trio thank Whedon with their gospel rendition of the “Ballad of Serenity.”

As of press time, The Letter Carrier is just a a few thousand dollars shy of its fundraising goal with five more days left.

Avengers: Age of Ultron
  • Movie
  • 150 minutes