This is by no means a concern of anything bad going on with my kitty, but just something I'm curious about. All other cats I've seen will fluff their tails and back fur up when they're scared or upset, but my kitty fluffs himself up when he's really happy. He purrs like a chainsaw, so I know he is, in fact, happy (he is also not long-haired, so I can tell when he puffs up). Does anyone else's cat do this? It's cute, but so strange. I guess it's the kitty equivalent of someone crying when they're happy?