Possible Clues:

• "Hop __": Dr. Seuss book
• 'Hop __': Dr. Seuss book
• See 16-Across
• Seuss's "Hop __"
• Classic Dr. Seuss book
• "Hop __": Seuss work
• Seuss's Hop ___
• Dr. Seuss' 'Hop --'
• ''Hop __'' (Seuss book)
• Dr. Seuss's Hop ___