Spinning Rapidash is the 9th episode of the 1st Season, in which Ashley and her Pokemon meet up with a herd of Rapidash and Ponyta, which after Squirtle accidentally blasts them with water, begin to go on a rampage!
WARNING: May contain Plot Details and Spoilers
Plot Description
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The Rapidash/Ponyta herd's Rapidash leader
The Rapidash and Ponyta chase them out of the forest and out until they all fall in a river, Misdreavus floating over top, looking down worriedly at them. Of course, Misdreavus (being a ghost-type) couldn't help them out, so it watched them climb their way out of the river. Piplup and Misdreavus both began to put the blame on Squirtle for the accident, which makes Squirtle very upset, and Ashley have to work to get her Pokemon to calm down.
Later when they were practicing again, they end up near the edge of the forest, and the herd come and try to attack them once again.

Rapidash running at them in Anger
Details
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The leader Rapidash happened to be the mother of quite a few of the Ponyta, which explained her almost motherly-like nature when one of them were harmed.
The move in this episode that Misdreavus attempted to learn but failed at doing so was Astonish.