Yes. It's infringement, but....unless you're selling tens of thousands of copies, no one is likely to care. If they did, you might have to take it down. But that's about it. No one is going to take away your house and car or anything like that. I think about the worse case scenario would be you'd be forced to turn over your profits. But again, the odds on anyone giving a tinker's damn is remote.
Yeah. Disney gives a tinker's damn. They've been known to send people to tiny craft fairs and stopping people from selling stuff made from Disney trademarked fabric. Like, don't make a potholder with Mickey Mouse fabric, or you'll get handed a nice little lawsuit.
And it's entirely possible to lose everything you have defending against a lawsuit. So, advice to not worry about being sued for trademark infringement (the Grinch likely is also trademarked, since there are secondary products on the market) is potentially dangerous to someone's livelihood and personal financial status.
About the only way one could get away with using something like the Grinch is to fall right into the parody lane, which might be hard to pull off. And even then, one would have to defend against a suit, which won't be cheap and could take years.