Any time you use the intellectual property of someone else, you need permission. Sometimes that permission is given automatically (such as a Creative Commons license) but other times it is individually licensed (where the user either pays the owner an agreed-to amount up front or provides an agreed-to cut of the revenue/profits). Resvlts has a license agreement with Disney -- the maker of those hats most certainly does not.
I suspect that the hat-maker thinks that they're being clever and has their weak defense all lined up (
"It's TOTALLY different, see? I switched the words! I can get away with it!"), but it's obvious they're ripping off Disney characters, and I doubt such a defense would hold up in court. Seeing how famously litigious Disney is, I suspect that it's only a matter of time before a Cease & Desist letter comes their way.
Also, I lol'd at "Round Mound of Screaming Loud"