Neil Gaiman and Joss Whedon

Joss Whedon and Neil Gaiman may well be the two most interesting people creating popular culture right now. Whedon is the man behind Buffy the Vampire Slayer and Angel, and he wrote and directed the science fiction film Serenity, which opens Sept. 30th. Gaiman created the instant-classic comic book Sandman, and he's the author of the new novel Anansi Boys, out this month. He has a new movie, Mirrormask, which also opens Sept. 30. They chatted on the phone together—chaperoned by TIME's Lev Grossman—about their work, their fans, their Klingon bodyguards and, of course, Timecop.