I rarely suggest anyone buy anything, but if you even remotely relate to my sense of humor I want you to buy, and I am not kidding, a 1971 made for TV movie called "Evil Roy Slade." I know what your thinking but trust me.
It may be the funniest movie I've ever seen.
There are people in this world that "get it" and there are those that don't. This movie, even with age, is the litmus test. The most amazing thing is that you can find out if your child, assuming he/she is over ten years of age, falls in the "gets it" category.
It's now on DVD.