Bill Watterson took two sabbaticals from writing Calvin and Hobbes: the first from May 1991 to February 1992, and the second from April through December of 1994. The next nine months worth of strips are from very early on.
Watterson authorized almost no merchandise at all; the only exception (I think) was a calendar one year. He never allowed stickers, clothing, or stuffed toys. If you see any C&H merch today, it’s guaranteed to be bootlegged.
If he had a mind to, Watterson could sue the people making it. That being said, I don’t get the feeling he expends much energy going after bootleggers.
The marks on his face? He’s turning red from the heat.