A while ago, I played a trick on my little sister.
Sometimes, she checks her e-mail on my computer and the password pops up whenever you type in her user name. One day, just as a joke, I logged in and changed her background. I didn't read any e-mails or anything. A couple of weeks later, out of curiosity, I log in again to find she had changed it back. I changed it again. This went on for a month or so before I decided to take it to the next level.
I logged in and wrote an e-mail to that same account saying,
"This is the ghost of your e-mail. You shall do what I say."
And I sent it.
She put it in Spam.
Giggling, I took it out of spam and wrote another one saying,
"I am not spam! I am the ghost of your e-mail and you can not escape me! Bwahahahahahaha!
I figured that after that she'd dismiss it as a joke, I didn't think hackers had a sense of humor.
She put me in Spam again.
This time I wrote,
"If you put me in Spam one more time, I shall put a curse on you family! Answer me!"
By this time, I was throughly enjoying myself.
As it so happened, I visited my sister that next weekend. I had brought my computer, and was trying to log in to her account again when I discovered she had changed the password. Bummed, I went to my other little sister to ask what it was, and when she didn't know, I thought I'd go directly to the source. When I gently broached the subject of e-mail passwords, little sister the first looked at me with big eyes and whispered,
"I think someone is trying to steal my identity! They keep logging in and sending me e-mails!"
Trying desperately to keep a straight face, I asked,
"So, what's you're new password?"
"Oh, it's--" and then she saw my face.
The gag was up.
I think she threatened to not talk to me for a week, but she eventually forgave me. The moral of this story is, if there is a mysterious person e-mailing you from your own account, it's probably me. Don't change your password.