The (delayed) Categories for Round 7 of BPD game 2 (Wuerthy) shines the light on Theodore "Doctor Seuss" Geisel, famed writer of children's books, savage political cartoonist, and all around nice guy.
The Secret Letter is
SCategories:
Category 1: Name the TITLE of any work of Doctor Seuss
Category 2: Name a fantastic creature invented by Seuss WITH A RHYMING NAME
Category 3: Name an invented character by Seuss that is supposed to represent a human being.
Category 4: Name an anthropomorphic (like a human or having human features) device or creature by Seuss
Category 5: Name a real life person of consequence to Doctor Seuss (other than himself or a member of his nuclear family).
Category 6: Name a periodical publication that Seuss drew cartoons for.
Again, when it comes to a title, it doesn't need to START with an S. And S can be a first or last name.