My cat's an indoor kitty. If he gained substantial weight, it would be because he could not go outside to play. However, as long as there have been housepets, there have been fat housepets.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"