How and where can I register a 'Chuck Norris' joke so that no one steals it?

[User]

When the jokes are published on a web page make sure to include a copyright claim, use a Creative Commons licence templates for example.

Before that:
Type the jokes on a page and get two witnesses to sign that you created the jokes, sign and date. Post the envelope to your lawyer, put on the envelope that it must not be opened. Once the letter is received instruct your lawyer to sign the back where the letter joins - this proves it has not been opened and proves the date the jokes were created (or the date our witnesses signed the page).

In the future if you need to prove the jokes you should start legal action against the any person who copies your jokes - or breaks your copyright claim. In court have the letter opened and bingo you win many monies.

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Joking aside a similar idea is used for songs and manuscripts.