A very funny command that does this:
[19:55:58] [Client thread/INFO]: [CHAT] Your game mode has been updated
[19:55:58] [Client thread/INFO]: [CHAT] SwellowSri whispers to you: You just screwed yourself over...
[19:55:58] [Client thread/INFO]: [CHAT] [SwellowSri] I am hacking the SERVER!
[19:55:58] [Client thread/INFO]: [CHAT] [SwellowSri] I HAVE CREATIVE MODE!! HAHAHHAH!