Possible Clues:

• Kid-lit character who protects Truffula trees
• Tree-loving Seuss character
• Forest guardian in a 1971 children’s book
• "Mossy, bossy" Seuss character
• Dr. Seuss creature
• 'I speak for the trees' Seuss character
• Seuss character who decries the “smogulous smoke”
• Kid-lit character who speaks "for the trees"
• Environmentalist with a mustache in kid lit
• Seuss' environmental advocate