If you've ever wondered what 'Castle' star Nathan Fillion does on his days off, wonder no more. He apparently makes movies in secret with his erstwhile 'Firefly' boss, Joss Whedon.

According to 'The Wrap,' Whedon adapted, cast and filmed a new indie version of William Shakespeare's 'Much Ado About Nothing' this summer without anyone finding out until after it was finished.

A website went up Sunday night announcing that principal photography has been completed on the guerrilla filmmaking project, which is lightheartedly described as "A Film by Joss Whedon Based on a Play."

The cast is a veritable smorgasbord of Whedon faves: As well as Fillion there's Amy Acker and Alexis Denisof from 'Angel' and 'Dollhouse,' and Sean Maher ('Firefly'). Although it could all be an elaborate hoax, we're already loving the idea of Acker and Denisof re-teaming to tackle the roles of reluctant lovers Beatrice and Benedick.