Potty Games - Riddles Only (Vol. II)

The answer is, indeed, the Whomping Willow!

Batman and Robin -comic cartoons,
Give a feeling of being over the moon.

Hint: the answer is dynamic, but not a duo -and not necessarily a "who".
Being "over" the moon is not a constant state, but does happen in phases.

The tree hits you with a BAM! POW! like you read in the comics, and during the full moon "Moony" goes underneath into the tunnel below.

Guesses: Animagi, Luna Lovegood, Lupin/Werewolf Lupin, Hagrid and Grawp, Sanguini, Fenrir Greyback, Mr. Lovegood, Wolfsbane potion, Marauder's Map, Crystal Balls, The moon's effect on Lupin, Riddikulus., Waddiwasi, Lupin teaching about Boggarts, Lupin in the shrieking shack, Lupin running with animagi.

Neville Longbottom!

Bubble, bubble, toil and trouble
Neville toils away in Potions class, but causes himself and others nothing but trouble.

Cauldron burn, explode into rubble
Neville burns and explodes cauldrons on a regular basis.

Black-bat fear and dismal career
Neville's greatest fear is Snape, the "black bat" of the dungeons, and Neville's experiences at Hogwarts are not illustrious (think leaving passwords around so Sirius Black can get into Gryffindor's dorm).

Will one day give way to a hero's cheer.
Yet 7th year, Neville gets over his fear, leads Dumbledore's Army, and kills Nagini, proving himself a true hero.

the maid for the Riddles.

You might call me "The Discoverer"
T'was me that found it out
And down the path I ran
To spread the word about.

Who am I?

Hint: Line three could read....."And down the hill I ran."

Guesses: Rita Skeeter, Quirrell, Moaning Myrtle, Tom Riddle, Jr. discovering Hagrid's pet, Snape discovering Werewolf Lupin, Gregorovitch, Mrs. Norris, Malfoy seeing Harry's head,

The maid was "the discoverer". She came in before breakfast and found the Riddles dead. She ran screaming down the hill (the Riddle mansion sat on a hill) to the village where she told everyone what she had found.