From Bulbapedia, the community-driven Pokémon encyclopedia.
Kingler's Day is the name of a Pokémon-based e-Reader application. It is a minigame featuring Kingler. Four cards are required to play the Kingler's Day application: Cloyster, Kingler, Goldeen and Magikarp.
In Kingler's Day, the player takes on the role of a Kingler. The objective of the game is to capture as many Goldeen and Magikarp in the pond as possible within two minutes. There are Cloyster in the pond as well, but attempting to capture one will stun Kingler for a few seconds. The game ends when the clock reaches 0:00. Kingler's Day is not a game that is won or lost; instead, it is a game where the player attempts to get the highest score that they possibly can.