Kelsey Grammer -- Brian Griffin's Gone But ... Sideshow Bob WILL Be Back

It's always darkest before the dawn -- "Family Guy" might have taken away our beloved Brian Griffin ... but Kelsey Grammer tells TMZ, Sideshow Bob WILL be making a triumphant return to "The Simpsons."

KG was out in L.A. this week when we got to chatting about Brian's death ... and conspiracy theories about the dog's return ... and Kelsey says Sideshow Bob ALWAYS comes back. "They've already killed him 20 times. He comes back a lot."