Mild 'n Wooly (Japanese: メリープとまきばのしょうじょMerriep and the Pasture Girl) is the 139th episode of the Pokémon anime. It first aired in Japan on March 16, 2000 and in the United States on February 17, 2001.
Spoiler warning: this article may contain major plot or ending details.
Team Rocket comes in sheep's clothing to relieve a kind Poké-shepherd of her Mareep flock. Ash and friends are eager to help, but will first have to convince the Mareep Trainer to have a little faith in herself.
Plot
While eating lunch in a grassy meadow, Ash and his friends encounter a Mareep, which the Pokédex describes as having a mild disposition and the ability to store electricity in their fleece. The Mareep smothers Pikachu, who retaliates with a ThunderShock. However, Mareep's thick fleece absorbs the attack and grows in size. Soon enough, more Mareep appear, and gather around Pikachu. He zaps them all, causing their wool to get very fluffy.
A young girl runs up, and attempts to get the Mareep to back off, but only one listens. Her mother and a Raichu arrive, and they succeed in freeing Pikachu from the flock. Ellen invites Ash and his friends over to her house, where she apologizes for the Mareep's behavior. It turns out that Mary was supposed to be watching the Mareep, but as she daydreamed about an upcoming festival for Mareep, they escaped. She wishes to enter, but her mother says she is too young. Seeing the tense situation, Brock offers the group's assistance on the farm, and Ellen happily accepts.
Later, Raichu and Pikachu are rounding up the Mareep, so they can be groomed in preparation for the festival. Team Rocket watches, with plans to sell the Mareep's wool to get rich. That evening, Mary and her Mareep, "Fluffy", continue to practice Thunder Shock outside. Ash is surprised by Fluffy's strength, and at Mary's insistence he agrees to battle her. The match begins, with Pikachu and Fluffy dodging each other's advances. Pikachu narrowly dodges Fluffy's Headbutt, but he is then startled by Growl. Fluffy's Swift attack hits, sending Pikachu flying backwards. The two electric Pokémon exchange Thunder Shocks. Pikachu soon loses power, but manages to dodge several Thunder Shocks. Fluffy soon becomes worn out from using too many electric attacks and faints. Mary is distraught. Ash takes a look at Fluffy, he notes that it is exhausted and will need a night's rest to recover. Mary admits that she was focused on winning her first battle ever, and Ash reminds her that she forgot to take care of her Pokémon. Before dinner, Mary apologizes to Fluffy, and tells it she has realized she is not ready to compete in the Mareep festival yet.
In the middle of the night, a storm approaches. Ellen takes the group and the Mareep out to a cliff, to collect electricity and make their fleece look good for the festival. As their wool is fluffed up and sparkling with electricity, Team Rocket attack, and net all of the Mareep. Ash tells Pikachu to attack, but Team Rocket captures him, too. Ellen's Raichu uses Thunderbolt, but the electricity is merely absorbed by a special panel. Upon trying again, the panel short-circuits, and the balloon crashes. Pikachu and the Mareep are freed, but Raichu is exhausted. When Team Rocket send out Weezing and Arbok, Ellen uses the Mareep to battle. However, they are not strong enough, and Pikachu is still stuck in the cage. Mary tells her mother to concentrate the herd's energy onto Fluffy: her Mareep becomes supercharged, and, with the help of Pikachu, sends Team Rocket blasting off again.
The next morning, Ellen gives her daughter an old Poké Ball, that once belonged to her mother, and says that she's ready to use Fluffy in the festival. Later, Ash, Misty, Brock and Ellen cheer Mary on from the stands, as her first battle commences.
She could also be based off of the character Heidi in the Japanese animation, Heidi, Girl of the Alps, with the Japanese name for Mary's Fluffy being "White" and Heidi's goat in the series being called "Yuki", the Japanese word for "Snow".