Blissey has a large egg shaped body, one half pink and the other white. The hair-like growths she had as a Chansey have curled up on her head. She has white, wing-like appendages where her arms meet her body and around her middle. She seems to have lost the tail she had as a Chansey. Like her pre-evolutions, she has a pouch on her stomach that holds an egg.
Gender differences
Blissey is a female-only species with no male counterpart.
Special abilities
It is said that anyone who takes one bite of a Blissey's egg will become unfailingly caring and pleasant to everyone. The eggs it lays are much more nutrient than common eggs due to the extremely high concentration of nutrients and also due to extra compounds that can't be found in eggs like endorphins and dopamine. Thus, only one bite of the egg is enough to relieve physical aches, revitalize and make anyone feel refreshed and happy. As a result, this is very beneficial in battle because the Pokemon not only feels revitalized but every pain vanishes so it can keep fighting for longer.
Blissey is known for their tremendous stamina. The main reason is that their heart and lungs are unusually large and robust. They are basically thrice the size of that of other Pokemon their size and their heart alone takes up to 3% of their body size. Blissey were also found to have amazingly large amounts of dopamine and endorphins, not only in their eggs, but in their bodies as well. Thus, they have the highest pain tolerance of all Pokemon and can still keep going even when suffering horrific injuries from battles which other Pokemon wouldn't be able to handle. Blissey are very hard to knock down because they have a large capacity to incur more damage than normal before fainting, especially if it isn't physical, so they are a common member in most teams.
Blissey is an extremely compassionate Pokémon by nature. If she sees a sick Pokémon, she will attempt to nurse the injured Pokémon back to health. Blissey's fluffy fur allows her to sense feelings of sadness. Upon sensing any sadness, this Pokémon will race to the source of the sadness, no matter the distance, and share her egg of happiness that instantly makes a person smile.
Blissey, the Happiness Pokémon. It is kindhearted and loves helping people. Blissey is the evolved form of Chansey.
In the manga
Blissey in Pokémon Adventures
In the Pokémon Adventures manga
A Blissey captured by Crystal and lent to Emerald for his Pike challenge appeared in the 27th volume. With her high Special Defense aided by a suitable nature served much use for the boy, and though she was eventually defeated, she was able to revitalize another borrowed Pokémon, a Rapidash, using Softboiled, with which the queen's Seviper was defeated by a devastating Overheat, winning him the match.
Blissey senses sadness with its fluffy coat of fur. If it does so, this Pokémon will rush over to the sad person, however far they may be, to share an egg of happiness that brings a smile to any face.
If it senses sadness with its fluffy fur, a Blissey will rush over to the sad person, however far away, to share an egg of happiness that brings a smile to any face.
Blissey's HP base stat is the highest legitimate single stat out of all Pokémon, at 255, giving her the ability to have the highest HP of any other Pokémon in the games (with a total of 714 HP if 252 HP EVs are added and if she has 31 HP IVs). Her HP base stat of 255 is the highest base stat possible, as all base stats are a single byte, the maximum value of which is 255 (1111 1111).
Coincidentally, three of them have the word "luck" in their names, referring to Chansey's Japanese name, Lucky. However, unlike the Lucky Punch and the Luck Incense, the Lucky Egg's Japanese name does not contain the word Lucky.
Blissey shares the same species name with Togetic. They are both known as Happiness Pokémon.
In Generation III, Blissey learns a move earlier than her pre-evolved form, Chansey. Chansey learns Egg Bomb at level 35, whilst Blissey learns it at level 28.
Blissey has the highest base experience yield out of any Pokémon, with 608 (255 in Generation IV and previous, where it still held the title along with Happiny, Chansey and Arceus).
Origin
She may be based on a nurse. Design-wise, she appears to have some physical similarities to Nurse Joy from the anime in both color and hair. She also bears slight resemblance to koalas considering their pouch, round appearance and 'hair growths' that look like koalas' ears.
Name origin
Blissey derives from bliss (happiness), combined with the suffix sey from Chansey, her pre-evolution.
Happinas may be a corruption of happiness, or it may be a combination of happiness and nurse. It may also involve 茄子 nasu (eggplant), referring to the egg theme of this evolutionary line.