Beginning with the original Nintendo DS's birthday function, all Pokémon games have, so far, had something inclusive for just this function, the most well known of which is the appearance of diamond dust, wherein on Junichi Masuda's birthday (January 12), it will appear in Snowpoint City.
In Generations I and III
The journals found in the Pokémon Mansion on Cinnabar Island reveal that Mewtwo was born on February 6.
In Generation IV
The description of Gracidea states that it is sometimes given out in bouquets for birthdays.
In Diamond, Pearl, and Platinum:
After defeating the Elite Four, Lucas/Dawn in Sandgem Town will ask the player if it is his or her birthday.
Diamond dust appears in Snowpoint City on January 12, Junichi Masuda's birthday.
In My Pokémon Ranch:. In the Platinum update, a new toy was added for when it is the player's birthday, the Birthday Cake, when activated, confetti falls from the sky around it.
In Generation V
In Pokémon Black and White and Black 2 and White 2:
The owner of the Pokémon Musical Theater will give the player the Prop Toy Cake.
The nurse in the Pokémon Center will ask the player if it is his or her birthday every time she is spoken to.
The mist on Route 14 and Route 15 will clear.BW
In Icirrus City, Aha, Wye, and Ditoh will give a special quiz.
In Generation VI
In both Pokémon X and Y and Pokémon Omega Ruby and Alpha Sapphire:
Upon entering a Pokémon Center for the first time on a birthday, the lights are dimmed, a party popper goes off and confetti falls from the ceiling.
In all Pokémon Centers, a birthday cake will be shown on the screen above the counter and a special version of the Pokémon Center theme will play. Every time a player goes to heal Pokémon, the nurse again wishes the player a happy birthday and states that she hopes the player will continue visiting for many years to come.
Other players will see a birthday cake marker beside the player's icon in the PSS. After tapping the player's icon, they may give birthday wishes by pressing a button on the touch screen that replaces the "Nice!" button. A Medal can be awarded for being wished a happy birthday on the PSS.
Visitors to the player's Pokémon-Amie space will leave up to three Supreme Wish Poké Puffs.
In Pokémon X and Y only:
Diamond dust falls on the area near the entrance of Frost Cavern.
In Generation VII
Upon entering a Pokémon Center for the first time on a birthday, the lights are dimmed, a party popper goes off and Pikachu and flower-shaped confetti falls from the ceiling.
In all Pokémon Centers, a birthday cake will be shown on the screen above the counter and a special version of the Pokémon Center theme plays. Every time the player talks to the Pokémon Center nurse, she wishes the player a happy birthday.
Diamond dust falls on the outside and summit of Mount Lanakila.
Events
In an event ongoing since Generation IV, players who visit a Pokémon Center store in Japan with an eligible Pokémon game can download a gift Pokémon on or near their birthday. Since Generation V, there is a special Birthday Ribbon which is exclusively for Pokémon received as birthday presents from Pokémon Center stores. In Generation VI and VII, they all know the event-exclusive move Celebrate, which congratulates the player.
