Castelia gym trainers all have air balloons on their pokemon

[kaikaol]

Did the castelia gym today and i noticed that all the trainers had air balloons on their pokemon, cant imagine why when none of them are weak to ground so thought i'd bring it to attention. 

[StrengthPolicy]

Because we all float down here, Georgie. 

[Rache]

Some trainer classes have themes / gimmicks for their items and movesets. Harlequins and Clowns have their teams hold Air Balloons, just as Hikers have HM moves and Breeders have breeding-related held items.

[Guest]

Epic plot twist would be having the event without update or announcement cause the things needed for it are already in the game, from a previous update.