Lately I've been having the urge to send my coworker and email a picture of my penis.
Are you serious, why would you think of doing that?
It's just a joke, I'm going to do it.
Sending pictures like that to a coworker is a bad idea. That is sexual harassments and you could get fired and arrested.
No, I won't get caught.
You most likely will get caught. You need to take a step back and really consider if you want to lose your job or not. Like I said this is sexual harassment and not good for the workplace.