Ash's Snivy

Biography
Snivy first appeared in BW007: Snivy Plays Hard to Catch!, where it was caught by Ash and the gang stealing food from them. Iris and Cilan believe that she deemed her Trainer unworthy of her and so abandoned them, after they witnessed her high-level attacks. Ash then chased after Snivy through all of the episode, using each member of his team in turn to battle her, however the majority of his team (Pikachu, Oshawott and Tepig) were affected by Snivy's Attract, forcing Ash to recall each of them. It wasn't until Pidove offered to battle did Ash manage to defeat Snivy, as her Attract had no effect on Pidove (due to her also being female, something Ash was not aware of until this point). Eventually, Snivy conceded defeat and allowed Ash to catch her.

She was sent out twice during Ash's five-on-five battle with Trip in BW010: A Rival Battle for Club Champ!. She first battled Trip's Servine and won with the help of her Attract. She then battled Trip's Frillish Ash had no knowledge of Frillish's Cursed Body ability, so commanded Snivy to use physical attacks, which led to their loss.

In BW028: Emolga and the New Volt Switch!, she battled against Bianca's Pignite after Iris' Emolga summoned it using Volt Switch. It later develops a rivalry with Emolga, as she is unimpressed with Emolga's attitude. It continuously uses Vine Whip to bring Emolga back after she tries to escape and also when Snivy showed the gang who had caused the fight between Ash's Pokémon. However, despite this, Snivy saved Emolga (as well as Axew and Oshawott) from a wild Simisear. Their rivalry was put on hold when Snivy and Emolga worked together to destroy a boulder that was about to crush the Simisear. However, the rivalry did not disappear, as shown when Snivy and Emolga looked quickly away from each other in disgust after catching each others' eye.

Ash used Snivy to battle against Trip's Servine again in BW034: Ash and Trip's Third Battle!. However, this time her Attract failed because of Servine's Leaf Tornado and she was defeated by Servine's Cut.

Snivy and Emolga's rivalry was shown again in BW035: Facing Fear With Eyes Wide Open!.

In BW042: Cilan Versus Trip, Ash Versus Georgia!, Snivy was used against Georgia's Pawniard during the second round of the Don Battle Tournament, however, she struggled against the powerful Pokémon, having Attract fail when Pawniard also turned out to be female. However, in BW043: The Club Battle Hearts of Fury, Emolga Versus Sawk! she managed to defeat Pawniard with Leaf Storm.

In BW052: Dazzling the Nimbasa Gym!, Ash used Snivy against Elesa. She went up against Elesa's Emolga. Since they were both female, so Attract proved to be ineffective. Emolga finally defeated Snivy with several powerful Aerial Ace attacks.

In BW055: A Maractus Musical!, Snivy was used alongside Pikachu and Tepig in Ash's very first triple battle against Tobio's Maractus trio. Even when their combinations of Thunderbolt, Flamethrower, and Leaf Storm, were being used, the battle was postponed due to Cacchin making them all fall down.

In BW057: Scraggy and the Demanding Gothita!, Snivy was happy to see Axew and Scraggy getting along despite them both losing in a battle. When Katharine's Gothita and Scraggy escaped and then followed by Axew in the middle of the night, Snivy followed them closely, and saves them from an attack caused by a wild Garbodor that Gothita disrupted. The next day, Ash used Snivy against Katharine's Gothita after he made a bet involving Scraggy, which ended in victory for her.

In BW063: Battling the King of the Mines!, Snivy was used in a Gym battle against Clay's Palpitoad. She used Attract to immobilized it and then hitting it with Vine Whip and Leaf Blade and finally defeated it with Leaf Storm. She went up against Clay's Excadrill and after her attacks were being blocked by Excadrill's Rapid Spin, Snivy got knocked out with a powerful Horn Drill.

In BW079: Evolution by Fire!, Snivy was used in Ash's battle against Shamas. She teamed up with Ash's Tepig to battle Emboar and Heatmor. She battled well despite the type disadvantage, but as Shamas was about to land a Flare Blitz/Fire Spin combo on Tepig, Snivy saved Tepig, getting knocked out in the process.

Trivia

 * Snivy seems to be the most level headed and mature Pokémon currently on Ash's Unova team.
 * It is suggested that Snivy is one of the few Snivy's who abandoned their previous trainers since they saw the trainer as unworthy or incompetent. Which could explain her high level grass moves and Attract, although it may be possible Snivy was strong before all this.
 * During Ash and Snivy's first encounter, Snivy displayed surprise at how Ash protected Pikachu and even thought about it a little. This could possibly mean Snivy had some troubled relation with a previous trainer.
 * Snivy was the only Pokémon on Ash's team to ever defeat Trip's Servine. After Pikachu fell to it, Snivy was able to defeat it. She later fell to Trip's Frillish.
 * She may have traits similar to Ash's Grass starters: being a prime battler as in Ash's Sceptile, being a protector as in Ash's Bulbasaur, if counted being a female Grass-type as in Ash's Bayleef and taking charge as in Ash's Torterra when it was Turtwig.
 * Snivy is Ash's sixth Pokémon to battle its evolved form. The other five were Pikachu, Sceptile as a Treecko, Corpish, Buizel, and Gliscor as a Gligar.
 * However, only Snivy, Pikachu, and Buizel defeated their evolved forms.
 * Snivy is Ash's second confirmed female Grass-type starter (the first being Bayleef).
 * But the only one that does not show any over affection for her trainer.
 * Snivy is Ash's only Pokémon to know the move Attract.
 * All of Snivy's Grass-type moves are also known by Ash's other Grass-type Starters.
 * Vine Whip is also known by Bulbasaur and Bayleef.
 * Leaf Blade is also known by Sceptile.
 * Leaf Storm is also known by Torterra and Sceptile.
 * Snivy has developed a rivalry with Iris' Emolga.
 * Interestingly, they are both the only female Pokémon currently on the main cast that know Attract.
 * The two have somewhat opposite personalities; Snivy is calm, collected, mature and willing to fight her own battles no matter how tough her opponent may be, while Emolga is childish, deceptive, lazy and unwilling to battle seriously and/or tricks or forces others to battle for her (by using Volt Switch).
 * Despite being with Ash all the time in Unova, Snivy has been rarely used in battle, it is possible that Ash only uses her to battle stronger opponents or male Pokémon.
 * Even though Snivy is a powerful pokemon, she has not been used much by Ash, just like his Palpitoad. She even had her first gym battle against Elesa after being with Ash for some time
 * Snivy is Ash's second Unova Pokemon confirmed to be female, the first being Unfezant.
 * Snivy seems to care about Ash's other Pokémon, an example of this was her saving Ash's Tepig in BW079.
 * Snivy was the the fifth grass-type pokemon to be captured by Ash. First was Bulbasaur, second was Bayleef, third was Sceptile, and fourth was Torterra.