William Earl administrator There are endless challenges to getting an indie feature-length animated film made: Lack of money, not enough time, fruitless rewrites, a vision that can’t get across the finish line. When asked what the biggest challenge was while making their upcoming comedy “Mars,” co-writers and voice actors Sam Brown and Zach Cregger can’t help but riff an answer to a question that inelegantly ignores the elephant in the room. “Well, Trevor died,” Brown says.