Check out Watch Your Contractions! by rogersgeorge. Here is an excerpt:
You might know this joke:
A guy visits the doctor’s office and has an examination.
Doctor: Looks like you have a henweigh.
Patient: What’s a henweigh?
Doctor: Oh, about five or six pounds.
If you don’t know the joke, it might take a second to get it. The humor hinges on the meaning of the…