In last Sunday's season 12 episode of Family Guy, 'Life of Brian', the show's writers stunned fans everywhere by killing off one of its main characters, Brian Griffin. Viewers who tuned in last weekend saw the talking pet dog brutally mowed down by a speeding car and later pronounced dead at a veterinary surgery, and the plot has not gone down well. Fans in their droves took to micro-social networking site Twitter to vent their fury, many of whom questioned if the show is still able to continue following the death. Irate viewers have even signed a petition to bring the alcoholic pooch back to life, which has already been signed by thousands. Some have even threatened to boycott Family Guy unless Brian returns to the adult animation, further proof that the angle has backfired spectacularly on creator Seth MacFarlane and his team. Others however aren't getting quite so worked up about things, and point out that, actually, Brian isn't dead after all, and maybe everyone should just chill out. Since Brian's 'death', a number of fan theories have surfaced online claiming the likable author is about to make a return from the grave later in the series. And here, we round up 5 of the best fan theories that prove Brian Griffin is still alive.