The series is dense with references to popular culture, including but not limited to science fiction and horror films, comic books, and video games. The Series 2 DVD release introduced the "Homage-o-meter", an alternative set of subtitles listing every reference and homage; the "Definitive Collectors Edition" boxed set introduced a similar subtitle track for Series 1. "2000 AD" artists Jim Murray and Jason Brashill provided the artwork for Tim's comic "The Bear", as well as other incidental artwork for the show. Tim's boss Bilbo wears a 2000 AD comic T-shirt whilst lecturing Tim about "".