Brock won Happiny's Egg in a Pokémon cosplay contest in All Dressed Up With Somewhere To Go! by entering his Croagunk dressed up as a Politoed. He was overjoyed to take care of the Egg, as he showed in the next episode when he rubbed his cheek against it affectionately.
In One Big Happiny Family!, while traveling on Cycling Road, the Egg began to glow. After taking it to a Pokémon Center and receiving assistance from Nurse Joy, the Egg hatched into Happiny. Soon after birth, she began crying for a stone to hold as a fake Egg. Brock found a white stone and polished it into an Egg-like shape for her. Team Rocket snatched Happiny away before he could give the stone to her. Eventually Happiny was returned to Brock and received her "Egg". Immediately after, she offered it back to Brock as a sign of friendship. He gave it back to her and then captured her in a Poké Ball.
Like most baby Pokémon, she became very attached to her Trainer very quickly. She was upset when taken out of Brock's care, and refused to cooperate with Team Rocket completely. Unlike Bonsly, however, she did not cry and fuss; she actually fought back against Team Rocket's Pokémon after Brock had been hurt: Happiny quickly knocked Meowth, Mime Jr., and Wobbuffet out of her way and flung Jessie's Seviper by the tail so she could get back to her Trainer, who she then launched several meters into the air.
Happiny has a cheerful personality, and is playful and energetic. Rather than walking, she is usually held in Brock's arms, much like Misty did with her Togepi. She also is sometimes seen sleeping or playing with Sudowoodo. Sometimes she was seen riding on Pikachu's back, as seen in A Maze-ing Race! and A Lean Mean Team Rocket Machine!.
Happiny has extraordinary strength for a baby Pokémon. Examples of this appear in Bibarel Gnaws Best!, where she carried many heavy boulders, and in A Maze-ing Race! and Crossing Paths, where in both she lifted and threw a big boulder. She saved Team Rocket, Dawn, and their Pokémon from falling in Journey to the Unown!, and saved Brock and Autumn from falling off a bridge by hurling them high through the air to the other side of it in Tanks for the Memories!.
She was also seen walking in Canalave City whilst lifting Ash's Grotle—who was comically tired due to its new form—with one arm in Jumping Rocket Ship!. She was also able to stop Dawn's Piloswine from rampaging in A Breed Stampede! with help of her strength. Later, on Leading a Stray!, when Mamoswine tossed Dawn up into the air, Happiny caught her just in time.
The only times where her strength was not enough were in Leading a Stray! (where she tried to pull off a tight manhole cover, but failed), and in The Psyduck Stops Here! (where she tried lifting a massive boulder, but collapsed under the weight and was knocked out). Any other time, she successfully brought out her special and uncommon power.
In Tanks for the Memories! Happiny learned how to use Secret Power in order to save Autumn and Ilta from a group of Beedrill. She also used Secret Power later on in the episode to put Team Rocket to sleep so that Brock and Autumn could get away.
Brock was going to use Happiny in her first battle against Marilyn's Shellder in Battling a Cute Drama!, but right before the battle started, Team Rocket interrupted and tried to steal Marilyn's other Pokémon. Before they could, Happiny was able to send them flying with her powerful Pound attack.
In The Brockster Is In!, a group of Tentacruel attacked the boat that Ash and his friends were taking back to Twinleaf Town. Their Poison Sting attack caused many of the Baby Pokémon to become poisoned. Despite all that Brock and the others were doing to help, they were not getting any better. After seeing this, Happiny evolved into Chansey in order to help the baby Pokémon. After she evolved into Chansey, she was able to heal Pichu and all of the baby Pokémon of the poison with her newly learned Soft-Boiled move.
Personality and characteristics
Happiny has shown to be a happy-go-lucky Pokémon and is very cheerful. Happiny is also cooperative towards her Trainer as seen when Brock was giving her a bath. Despite her size, Happiny has been known for lifting most heavy objects with the exception of two instances as the objects were either too heavy or could not be carried by any means necessary. She has retained the happy and cheerful personality after evolving.
| Using Secret Power|
as a Happiny
| A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.
- Chansey was first revealed as a Happiny in a Japanese movie poster for The Rise of Darkrai.
- For The Bells are Singing!, Professor Oak's lecture is about Brock's Happiny.
- As a Happiny, she was the first among the main characters' Pokémon to have been given and kept a held item, in this case, an Oval Stone made by Brock.
- Although Chansey learned Secret Power as Happiny in Tanks for the Memories, she hasn't used the move since that episode.
- Of Pokémon obtained during the Diamond & Pearl series, Happiny took the longest to evolve, at 152 episodes.
- Out of all Pokémon belonging to the main cast, Happiny also took the longest to evolve while her Trainer was continuously part of the main cast, with said Pokémon never leaving the Trainer's possession.
- As a Happiny, she was the only one of her species to appear in the anime.
- She is the only one of Brock's Pokémon that does not share a type with another Pokémon he currently owns.
- In the ending theme Let's Join Hands, she appears as Happiny rather than a Chansey. This also occurs with Steelix appearing as an Onix.
For more information on this Pokémon's species, see Happiny and Chansey.