Most of us who have ever watched a cartoon have seen Popeye or some other totally malleable character squeeze through a pipe—the humorous aspect being that metal pipes usually don't give way and take on a bulge for sailors real or imagined.
Because a cartoon is a form of animation, there's no reason a bulging pipe cannot be a GIF animation.
You just have to know a little about displacement mapping to displace the ordinarily unyielding form of a pipe.
In the steps coming up, you'll use a file from the companion CD, and learn how to seize some of the power of the Displace command, admittedly a command that in all Photoshop books gathers a little dust. You simply need ...