Ash's Unfezant is a bird Pokemon caught by Ash in the Unova Region.
As he has done in every other region he has traveled in before, Ash usually catches a Flying-type Pokémon early in his journey. Pidove was caught soon after Ash's arrival in Unova. In Enter Iris and Axew!, shortly after a flock of Pidove had escaped when Ash had failed to capture one of them, he noticed her pecking at the ground, and engaged her in a battle. She managed to put up a good fight against Ash's Pikachu , until the Electric Mouse Pokémon used his powerful Iron Tail and Thunderbolt attacks, which caused her to faint. Ash threw a Poké Ball and successfully caught her. Later on, for the first time, Pidove was sent out in an effort to save Pikachu and Iris's Axew from Team Rocket's capture. However, as she was still weak from her battle with Pikachu, she was quickly defeated by Jessie's Woobat's powerful Air Slash attack. She was later healed at the Pokémon Center, along with Pikachu and Axew.
Unfezant is occasionally used by Ash to find and track certain Pokémon. She helped Ash find two Darumaka in Saving Darmanitan From the Bell! and a wild Snivy in Snivy Plays Hard to Catch!, playing a dominant role in the Grass Pokémon's capture. At the time, Pidove had followed Snivy throughout from the time she escaped using Leaf Storm. As she witnessed all of Ash's other Pokémon (Pikachu, Oshawott and Tepig ) fall to the Grass Snake Pokémon's Attract, she volunteers to battle Snivy. When Snivy attempted to use Attract on Pidove, Pidove was unaffected as she was female (a fact of which Ash had been completely unaware of, despite Iris and Cilan's assumptions that it was his strategy). After a hard-fought battle, Pidove weakened Snivy enough for her to be captured by Ash.
In A Rival Battle for Club Champ! she was briefly used by Ash in a 5-on-5 battle against Trip's Frillish. She tried her best but was taken by surprise by his Water Pulse, and got knocked out in the process.
In A Venipede Stampede!, Ash used her to help send the Venipede that took over Castelia City to the park in the center of the city. Although things started well, she was almost hit by a Sludge Bomb and was only just saved by an Air Cutter from Trip's Tranquill. She then helped remove a few more and then suddenly evolved into Tranquill herself. As a result of her new stronger form, Tranquill was able to clear out the last Venipede with a powerful Gust alongside help from Trip's Tranquill's Aerial Ace attacks.
In Archeops In The Modern World!, Tranquill was used to help a newly revived female Archen learn how to fly. After Archen evolved into Archeops, Tranquill defended her from Team Rocket and they said their goodbyes, up in the air, once Archeops found some others.
Ash used Tranquill to battle Skyla in An Amazing Aerial Battle!. She was first sent out to battle Swoobat who had already defeated Krokorok before her. After their Gust and Air Cutter attacks proved to be dead even, the battle took to the sky where Tranquill tried to get the upper hand with her newly learned Wing Attack, however Swoobat was able to swiftly dodge the barrage of Wing Attacks until it was finally beaten by Tranquill's powerful Air Cutter attacks, as they descended to the ground. She then fought Skyla's Unfezant, but with none of her attacks even touching Unfezant due to her lack of speed, Tranquill started to show signs of tiring after narrowly escaping a barrage of Air Slash attacks and was called back to her Poké Ball, while Pikachu took her place. She was brought back out again after Pikachu had lost to Skyla's Swanna despite having the type-advantage. During the battle with Swanna, she was able to hit Swanna with a powerful Quick Attack and Air Cutter causing Swanna to fall towards the Gym; she then rushed past Swanna and tried to hit it with Gust, however Gust was vastly overpowered by Swanna's Hurricane attack. While it seemed as if Tranquill had been knocked out, she began to glow and evolved into Unfezant. With her new found power and speed, she was easily able to dodge Swanna's powerful Brave Bird attacks and with the help of her newly learned Aerial Ace attack, was able to defeat Swanna with one extremely powerful hit, winning her the battle and earning Ash his sixth Unova Badge.
In Rocking the Virbank Gym! (Part 1), Ash sent Unfezant out as his second Pokémon in his 6-on-3 Gym battle against Roxie, where she faced Roxie's Koffing. Unfezant started the round with a Quick Attack, that made a direct hit. Koffing then attacked back with Will-O-Wisp, but Unfezant sent it back with a Gust before attacking with Air Cutter. Koffing, however, avoided the attack and launched a Sludge Bomb, which hit and poisoned Unfezant. Though she was weakened, Unfezant was able to withstand Koffing's Clear Smog and fight back. She was, however, unable to stand two consecutive Gyro Balls, and was finally taken down.
In Unova's Survival Crisis!, Ash used Unfezant along with Pikachu to battle the Kami trio after Giovanni took control of them to keep Ash and friends occupied. After Iris's Dragonite was injured and fell to the ground, Unfezant and Pikachu managed to save Iris and Dragonite from being attacked by Thundurus. When Meloetta was finally freed from the tomb, Unfezant grabbed it so that it didn't fall and get hurt.
In BW107, Ash used Unfezant in his Vertress Conference battle against Cameron and his Riolu . Despite Unfezant having the type advantage, Riolu proved to be a powerful opponent, being able to dodge both an Air Cutter and a Quick Attack before landing on Unfezant's back and serving a close range hit with Force Palm. Ash told Unfezant to shake Riolu off and then strike back with an Air Cutter. However, the Emanation Pokémon was able to dodge the attack and then use Copycat, hitting Unfezant with her own move, before serving another hit with Vacuum Wave. Unfezant tried to attack with Aerial Ace, but the Flying-type's last effort was avoided and countered by Riolu's Circle Throw, which sent Unfezant flying into the arena wall, knocking her out.