Paul catches a Gliscor.
The featured town is apparently located on Route 215, which is one of the routes where wild Gligar appear in Pokémon Diamond and Pearl via the dual-slot method.
Ash's Turtwig masters Energy Ball.
Ash capturing Gligar is similar to how he captured Squirtle back in Kanto, in that both were part of a group of Pokémon of its species causing trouble for a town, joined because it wanted to go with Ash, filled Ash's party with six members, and was captured in the twelfth episode of the season, two episodes before Ash met up with the region's third Gym Leader.
Ash catches a Gligar.