Oh, the possibilities of the brain... WOW! There's a jumbled cloud of information in every cranium.

i'm not a hundred percent positive on the exact legal rights of cranium imagery but the characters were created by http://garybaseman.com/ and i don't think you should be using it in your design. try to be more original, the t-shirt doesn't need cranium owned imagery in it.

i like it anywho.
but yes, it should not break rules :(
$3.5

I don't think those are the same characters as that basemen dude just cause they have big eyes and play-dohish heads. By the way, did you mean to reference Joe Versus the Volcano in the title? Because if you did (sub-consciously or not), i might have to bump my score up an extra point.

This needs more colors and be bigger, maybe make it with more cloud-like or more tree-like, but pick a direction and go with it.