I remember having a huge fight with my roommate about TimeTurner's fan name should be written,Doctor Hooves or Doctor Whooves
I think its Doctor Hooves because Hooves already has the same pronunciation as Doctor Who-ves but to each they're opinions!
I also heard him being called Doctor Whoof among other names...
I saw the same shirt on WeLoveFines,i think they have permission to sell them but Hasbro doesn't get the profit from the sales.
If anything,i think the company selling the merchandise pay for said permission.