Important Legal Question!

So I have been bouncing around the idea in my head to get a graphic t-shirt made for showing how to do the Manderville dance. Would there be any legal issues with this idea, even if I own the only one in existence?

I can't say for certain, but if you're just making one for yourself and not distributing anything, I think it's fine. It'd be on par with "fan art" I think.

I want to say as long as you aren't selling said T-shirt you should be fine yeah?

You can always tag SE to have the credit, just put it inside a tag inside the shirt so it wouldn't be visible normally, but it would be there if the problem arises.

Are you worried that the SE bounty hunters will find you, rip the shirt off of your back and throw you in a wagon to be carted off to jail?

Unless you're planning on selling it, gaining some sort of commercial success, or bragging about your awesome shirt on a public Square-Enix owned forum, you'll be fine.

The Manderville Dance is the copyrighted material owned by Square-Enix and whatever parent corp. Accordingly, they have rights in derivative works, displays, yada yada.. all that good stuff found in § 106 of the Copyright laws. Such a shirt would undeniably be considered a derivative work. The moment you start selling it, SE has every right to send a cease and desist letter to your house. Whether they do or not is another story (see Etsy which seems to be built on copyright infringement :P ).

(additionally, you're arguably prohibited from arranging a flash mob to perform the Manderville :( )

Why..........

What they said. Unless you plan on selling it, that would be fine. It is the conceptual equivalent of drawing a chocobo on your school notebook; nobody is going to send you a C&D order for something so trivial and, most importantly, private. It is private use with no commercial intention for distribution and/or profit.

And yet you have dozens of websites selling t-shirts that parody video games that include using characters from the various IP's and there's no legal fall out from that. OP should be fine.

If the Manderville goes viral on Youtube I know who to blame. :P