Happiny loves to pick up eggs it finds and put them in its pouch, to the annoyance of Pokémon who laid those eggs. Happiny usually gives the egg back, but if the offending parent is too rude, it will just run off.

Travelers who spy a shadow darting from hiding place to hiding place are relieved when it’s revealed to be a Chansey.
SURGEON CHAMPION’S WARNING: Contact your Pokémon Center if you or a loved one are suffering from Chansey egg addiction.

Many Blissey choose hospitality work over battling. Only Blissey with a very strong bond with their Trainer will follow them into battle.