nobody said that in the hobbit. the book you're talking about is The Lorax, in which a small brown creature, the Lorax, indeed, speaks for the trees
'The Hobbit' of course!
By 'the hobbit', I'm supposing you mean Bilbo Baggins in The Hobbit? If so, he faced Smaug the Great Dragon, King of the Lonely Mountain.
They don't exist. They are part of the Tolkien mythos.
not really, they prefer homes in burrows in the ground.
Your average mosquito.
No, there is no Agrog in The Hobbit or The Lord of the Rings. There is a giant spider named Aragog in Harry Potter and the Chamber of Secrets.
Tolkien's vast imagination.
no he killed his mate for a ring
no
The creature would be hobbit. They were shorter than dwarves and lived in the Shire.
Dart Frog