Glalie was first seen in Let it Snow, Let it Snow, Let it Snorunt! on Izabe Island as a Snorunt. It followed Ash and the gang through the snow to the Pokémon Center, where it began to cause trouble and stole Ash's Badge case. Once Ash, Pikachu, and Corphish cornered it Snorunt froze Ash's Stone Badge, threw it into the air and escaped with the rest of the Badges using Double Team. Snorunt then started dropping the Badges one by one to make its "game" more interesting. After a small meeting with Team Rocket it froze Ash with Icy Wind and left the Center through the window into an oncoming snowstorm. Ash followed it and they ended up lost in the snow. After Ash got knocked unconscious by protecting it from a small avalanche, Snorunt took him to a cave, safe from the blizzard. After Ash awoke, Snorunt handed him some apples. As Ash began to trust the mischievous Pokémon, Snorunt ran off into the blizzard with his hat, so it could lead the gang to where Ash was. Reunited, the gang scolded Snorunt and asked for the other Badges, before being interrupted by Team Rocket capturing Snorunt and Pikachu. Snorunt quickly escaped and saved Pikachu before battling Team Rocket's Pokémon. Later on, Snorunt still refused to return the Badge case, so Ash battled it and subsequently caught it. It was introduced to the gang's other Pokémon at the end of the episode, where it continued to prank everyone.
In the next episode, Snorunt joined Max in his effort to get an unwell Ralts to a Pokémon Center. During the journey, Snorunt used Icy Wind to make ice packs to battle Ralts' fever.
In The Great Eight Fate! Ash chose Snorunt and Pikachu as his first two Pokémon in a Double Battle in the first round of the Sootopolis Gym battle, going up against Juan's Sealeo and Seaking. Pikachu used Thunderbolt on Sealeo, but Seaking used Horn Drill to reflect it back to Snorunt. Pikachu then used Thunder, but Seaking used Horn Drill to reflect the attack to Snorunt again, but this time Pikachu protected Snorunt, taking most of the damage. Sealeo then used Blizzard on the two - Pikachu took a lot of damage but Snorunt barely felt the attack and jumped around happily. Snorunt then used Icy Wind to stop the Blizzard, creating an ice pillar that blocked everyone's view. When Sealeo and Seaking destroyed it, ice shards were sent up in the air which Ash had Snorunt and Pikachu jump on to attack. Seaking then used Hyper Beam on Snorunt and Sealeo used Aurora Beam on Pikachu. Pikachu was able to dodge the attack but Snorunt was not, and the Hyper Beam knocked it out.
In Date Expectations!, Ash began trying to teach Snorunt Ice Beam. While learning the new move, Snorunt ended up freezing people multiple times, including its Trainer and Anthony. Finally in Rhapsody in Drew, Robert gave it some words of advice on how to focus the attack while battling Team Rocket during the Grand Festival. Snorunt then evolved into Glalie and sent them blasting off with its newly mastered Ice Beam.
Glalie and Ash in the Ever Grande Conference
Glalie had several battles in the Ever Grande Conference and proved to be quite a powerhouse in Ash's team. In Shocks and Bonds, it teamed up with Grovyle to battle Clark and his Pokémon, Quilava and Charizard, although both of Ash's Pokémon were at a type disadvantage. Glalie's Icy Wind did not damage either Pokémon but managed to hold off a Heat Wave. Grovyle and Quilava both went down, leaving Glalie against Charizard. Glalie froze up part of the battlefield so it could avoid Charizard's Flamethrower, but ended up being knocked around its own ice pillars. Glalie managed to change this to its advantage, using the momentum to raise its speed and used a high speed Headbutt to flatten Charizard and give Ash the win.
Ash used Glalie as his third Pokémon in his Full Battle against Katie. It went up against her Dugtrio. Dugtrio used Dig but Glalie used Headbutt on the ground, forcing Dugtrio to emerge and dealing damage. Glalie then used Ice Beam, knocking Dugtrio out. Glalie then went up against her Misdreavus. Glalie used Ice Beam but Katie had Misdreavus take the attack. Glalie then used Headbutt, scoring a direct hit. While being hit Misdreavus used Destiny Bond. The Headbutt then defeated Misdreavus but due to the effect of Destiny Bond Glalie was also knocked out.
In Choose It or Lose It!, Ash used Glalie as his sixth and final Pokémon in his Full Battle against Morrison, going up against his final Pokémon, Metang. Glalie used Headbutt while Metang used Take Down, with Take Down dealing more damage. Glalie used Ice Beam, which Metang was able to redirect with Confusion, hitting Glalie. Glalie's Ice Beam was reflected a second time, but Ash saw this coming and used Icy Wind to redirect the attack back to Metang again, hitting it. Glalie hit Metang with Headbutt, but Metang countered with a super-effective Meteor Mash. Glalie used Headbutt again, spinning to increase its power, while Metang used Meteor Mash. Just before the collision Glalie ducked, avoiding the Meteor Mash and hitting with the spinning Headbutt, knocking out Metang, winning Ash the battle and moving Ash to the next round of the Victory Tournament.
Later, Ash used Glalie as his first Pokémon in his Full Battle against Tyson, going up against his Sceptile. Glalie used Ice Beam while Sceptile used Solar Beam, creating a massive explosion. In the next episode, it was revealed that this explosion knocked out both Pokémon.
Kanto Battle Frontier
In The Right Place and the Right Mime, Ash left Glalie at Professor Oak's Laboratory before he went to challenge the Battle Frontier.
Glalie returned to Ash's team in An Old Family Blend! for the Lily of the Valley Conference. Upon seeing its Trainer, it froze Ash with Ice Beam, which Torkoal later thawed out. In Working on a Right Move!, Glalie was seen training with Torterra and Infernape before Ash's battle with Conway. Ash was initially going to use Glalie because of its power to try to overwhelm Conway, but changed his mind as he knew that he couldn't depend on sheer power alone. In the end, Glalie was not seen participating in the Lily of the Valley Conference.
Glalie was reunited with Ash in The Dream Continues!, where it and the rest of Ash's Pokémon posed in a group photo with him.