1. The second your
“original” creations are affixed to a tangible medium (written, drawn, sculpted, filmed, recorded, etc.) they are protected by Copyright law.
2. Because of this you do not
have to register your Copyrights, but doing so creates a physical record of your ownership and grants you to the ability to claim damages should you have to go to court over an infringement (it also makes it a lot easier to prove that you are the owner of the original works).
3. The “Poor Man's Copyright” (mailing a copy of your work to yourself and leaving it sealed in a canceled envelope)
DOES NOT WORK! The post office will process and deliver unsealed, empty, envelopes (which means that there is no way to prove that the contents of the envelope predate the envelope's processing date).
I don't know who or what “Mistah FAB” is, but if you have any other works containing him that predate your stolen imagery you can at least attempt to prove that you are the creator should the need arise. If you're that concerned about it though, I would suggest registering your Copyright.
There are no trick or loophole ways to register your Copyright. The ONLY way is the official way…
http://www.copyright.gov/