Annie

Annie is not a Yordle, she is a human Noxian child according to the official LoL wiki.

Annie is a child with great power who has enchanted a bear in the forest at just the age of two! With Tibbers on her side, She has a unique power, enough to incinerate her enemies to ashes. Annie was a child of the most powerful mage in noxus but ther parents didn't agree with the evils in Noxus so they began an exodus. Now Annie and her parents are independent from Noxus and she has even met a yordle friend, a mummy - Amumu.

Annie Builds/Basic tips
Annie is a nice mid laner. Always Charge your stun in-case of enemy ULT (ex. Karthus, Katarina,Ezreal etc.)

Do not forget to learn Annie's 3rd ability (Molten Shield) because it is useful in fights and in defense which gives you bonus armor and magic resist

Tibbers is pretty useful against a 1v5 situation especially if tibbers landed with a stun can be a game changer and Gank control

Annie is Strong in the late game be sure to maximize her Q and W early to bring down enemies with a massive damage

Counter Picking as Annie
Always use Annie against champions like Katarina, Akali, Teemo, Fizz and other squishy champs