Ash invents the Counter Shield technique.
This is the first episode where a Pokémon Contest and a Gym battle are depicted in the same episode. It is also the first episode to feature a Pokémon Contest in which neither May or Dawn participate.
As of this episode, every member of Ash's Sinnoh team, other than Gliscor, has been used in at least two Gym battles; and Grotle, Pikachu, and Buizel have been used in three. This also includes Aipom, who was eventually traded and evolved.
Although Ash invented the Counter Shield technique for attacking and defending at the same time, it was Fantina who gave it its name in this episode.
Ash has an official Gym battle against Fantina and wins, earning the Relic Badge.