Crossing the Battle Line! (Japanese: ヒカリはじめてのジムバトル！！ Dawn's First Gym Battle!!) is the 15th episode of Pokémon: DP Battle Dimension.
The time has come, for Dawn. While Ash gets busy for his turn against Maylene, and learning how to master the move Brave Bird, Dawn has the honor of battling Maylene. Her plan, to rebuild her confidence in herself and in Maylene. Will her plan succeed, and will Staravia master Brave Bird in time for Ash's Gym Battle?
Maylene would like to battle tomorrow, which suits Dawn just fine. Later, Buizel trains Piplup for the battle. Reggie asks Ash if they should as well, so Ash rushes to train, but he wishes luck to Dawn in her challenge. Brock asks Dawn which Pokémon will she use and she picks Piplup, Buneary and Ambipom. They notice Ash is training Staravia. Ash and Staravia watch as Reggie's Staraptor uses Brave Bird to smash a boulder. Reggie warns Ash using the move can cause damage to the user. Staravia dives in, but fails to perform Brave Bird. Reggie thinks they should have a moving target to improve concentration. Ash volunteers to be the target, wanting Staravia to be stronger.
Ash runs and Staravia uses Brave Bird, almost hitting Ash. Dawn saw this and wants to go to her training. Brock tells Reggie this is an example how Ash trains his Pokémon. Reggie remarks Ash is the opposite of his brother, Paul. Reggie wants to know why would Dawn battle a Gym Leader if she is a Coordinator, but Brock knows Dawn wants to awaken Maylene's spirit again. Maylene meditates, but is hungry. Lucario is angry for this, but Maylene promises to accept the challenge as seriously as it can get. Team Rocket sees this and Meowth would like to get Lucario, but Jessie does not want a Pokémon that can break them. Instead, she plans to get a weaker Pokémon.
During the night, Ash and Dawn exchange their training experiences. Dawn is nervous about the Gym Battle, and so does Ash every time he has to. Brock knows how it is to feel like Maylene - at first, he did not know what to do, but after learning from his challengers, he became wiser through the Gym Battles. Brock mentions Reggie will be there to see the battle. Next day, Team Rocket spies and see the twerps entering the Gym and are surprised to see the female twerp going to battle. Maylene thanks Dawn for challenging her and sends Meditite. Dawn has some doubts about battling, so Ash goes to inspire her and Maylene. Dawn sends Buneary to fight it.
Buneary bounces, but Meditite uses Detect to counter. Meditite uses Drain Punch, affecting Buneary. Meowth asks if they should activate the Plan B Jessie suggested, but she wants to hold it a moment. Buneary freezes Meditite via Ice Beam, but Meditite uses Confusion to use the ice and turns it against Buneary. Meditite uses Confusion on Buneary and drops her, but Buneary bounces and collides with Meditite, who used Drain Punch. The drain Punch causes Buneary to be defeated. Dawn sends Ambipom. Ambipom uses Swift and the stars spin around Meditite, then strike, hitting it. Meditite uses Drain Punch, but Ambipom blocks it using her tail. With two strikes of Double Hit, Meditite is defeated.
Maylene senses that Dawn fights as it were a Contest, so she goes to stop her in that, sending her Lucario. Ambipom uses Double Hit, though Lucario uses Bone Rush, countering her move and retaliating. Ambipom is defeated and sends Piplup. Piplup uses BubbleBeam, but Lucario dodges and uses Aura Sphere. Piplup is pushed away, but not defeated. Piplup engulfs Lucario in a Whirlpool and charges with Peck, though Lucario counters using Metal Claw. Piplup uses BubbleBeam, but Lucario evades and touches Piplup, then uses Force Palm, hitting it. Team Rocket witnesses this and Meowth knows catching it would mean get hit by its moves. Lucario uses Aura Sphere, but gets pierced by Peck and hits Lucario. Lucario uses Aura Sphere, but gets collided by BubbleBeam. Piplup charges to peck, but sees Lucario's gone. Lucario jumped and in a moment, attacks with Force Palm, defeating Piplup.
Dawn rushes to Piplup and encourages it. Ash marks they fought well, tempting Ash to challenge Maylene. Maylene thanks Dawn, as she now forgot about her fears. Dawn tells Ash would like to challenge her, and it won't be easy. Maylene decided to continue being the Gym Leader, knowing how fun can it be. As soon as Staravia learns Brave Bird, Ash will come and battle with her.
- Challenger!! can be heard when Ash is teaching Staravia Brave Bird.
- Music from Lucario and the Mystery of Mew can be heard during Dawn's battle.
- This marks the first time a main character other than Ash competed for a Gym Badge. Coincidentally, Cilan Takes Flight!, also the sixty-seventh episode of a series, also features a main character other than Ash battling a female Gym Leader.
- Professor Oak's Pokémon lecture: Ash's Chimchar
- The dub title is a play off the saying "Crossing the line".
- Team Rocket doesn't blast off or recite their motto in this episode.
- When Ash and Dawn are talking on the balcony, and the camera switches to Brock's Happiny, her outgrowth on top is missing.
- When Dawn is battling Maylene, she says that her Piplup's Peck attack is super effective against Lucario. However, Peck would only deal neutral damage due to Lucario being part Steel-type.