Body Preservation

Okay, listen up, buttercup, because you seem a little slow on the uptake. You wrote this joke, so I'm gonna assume you're not the brightest bulb in the box. The joke uses a play on words. "Maintain a good body" usually means working out and eating healthy to stay fit. But, the punchline shifts the meaning to physically preserving a body in a freezer. It's funny because it's unexpected and a bit morbid.