Any big company that manages a well known brand has to look out for its marks though, if for no other reason than to demonstrate that they have value. I doubt Jimmy had anything to do with it. They have lawyers to look after this sort of thing.
Back in the late 80s Disney was being chastised for "defending it's trademarks" when they filed suit against a town in Canada for using Winnie the Pooh and they also sued a chain of daycare centers in South Florida for putting Disney characters on the outside of the building. In the latter case Disney claimed that those characters implied Disney's support, approval, involvement in the daycare centers.
At issue with Trademarks, as I understand it, is that when a company does not defend them they can...after a period of time...be considered part of the public domain.
Considering the value of Mickey and friends to Disney (and of Jimmy Buffett's "brand" for that matter to Buffett) you can understand why they would be vigilant in the courts.
While I'm no attorney, I can clearly see the huge difference between using actual Disney characters painted on a building and the term "carrothead". But, I can also see why Buffett would go after the term. I bet they wouldn't be as upset if carrot didn't sound just like parrot. I'm sure he doesn't go after the Green Bay Packers for having cheeseheads.
No one is "upset" over anything. Claims like this are based on two factors: That the infringing mark can cause confusion in the marketplace, and that infringing mark profits from similarities to an existing mark. Most case law in the US seems to focus on the confusion part, but I've read about cases that were reinforced by the profit from another mark angle as well.
I'm no attorney...but I did stay at a Holiday Inn Express once. (Actually, I was just re-reading one of my many Disney books that talked at great lenght about those lawsuits.)
I'm sure if a new softdrink came out called KokaCola you would see pretty swift action out of Atlanta. Or, if there was a new chain of restaurants called Kenttuckey Fried Chicken. You get what I'm saying.
It is easy to bash large companies. In fact, it is good sport. But, sometimes, those companies aren't as "evil" as it might appear they are.
^ Yeah, that's what I'm talking about. Carrothead is clearly trying to pan off of the parrothead recognition. Cheesehead is not. If they had the Bugs Bunnyhead club, I bet no one would have said anything.
But he does not "own the rights" to each and every ________-head. He may have some trademark over "parrothead" in regards to a fan club or merchandising or whatever,but "Carrothead"? No way. What about Pothead, or Radiohead, does he "own" those trademarks too? It's a common-used phrase and besides - Six Flags probably has Carrothead branded as a trademark as well - do we know for sure that they don't?