The High Five first appeared in Mounting A Coordinator Assault. Ash and Dawn did this impulsively in the corridors at the Jubilife Contest, which Ash was persuaded to participate in by Dawn, though he typically does Gym Battles. A sign of encouragement and a trademark of Pearlshipping, the High Five has appeared countless times throughout the DP series. It also appeared in the BW series during Dawn’s cameo.
Ash and Dawn are the only main characters to trade Pokémon, as seen in Throwing The Track Switch. Ash is known to be very protective of his Pokémon. The fact that he traded with Dawn shows his trust in her.
Dawn dressed up as a cheerleader for Ash’s Gym Battle rematch during his first Gym challenge. She does this three times over the series run. It is noted that Ash never loses when she does this. It is also noted that Gary Oak had cheerleaders during the first Kanto series, when he was a total troll to Ash and had his own Corvette. None of the other females have taken this length to support Ash.
While all the other main girl cameos started with the girl saying they missed Ash, rather formally. Dawn, on the other hand, sneaks up behind Ash and plays a trick on him, showing their ease around each other.
Gym Battles and Contests:
As said earlier, Ash has participated in a contest. But did you know that Dawn has challenged a Gym, too? She challenged the Veilstone Gym, where the insecure Maylene was leader. The purpose of her Gym challenge was for Maylene to regain her confidence so that Ash could challenge her. This "role reversal" shows just how in sync the two are with each other.