The Peter Pan syndrome refers to the supposed psychological phenomenon of immaturity among some men, who, like the fictional character, remain childish and fail to assume appropriate adult social roles and responsibilities.
In the USA they are generally called the Boomerang Generation, a term applied to the current generation of young adults in Western culture. They are so named for the frequency with which they choose to cohabitate with their parents after a brief period of living alone - thus boomeranging back to their place of origin.
Parasite single is a Japanese term for people who live with their parents until their late twenties or early thirties in order to enjoy a carefree and comfortable life. In English, the expression sponge orbasement dweller may sometimes be used.
The expression is mainly used in reference to Japanese society, but similar phenomena can also be found in other countries worldwide. In Italy, 30-something singles still relying on their mothers are joked about, being called Bamboccioni (literally: grown-up babies). In Italy they are also called "Mammoni", which in Italian means mama's boy. More than half of the single Italian men in Italy still live at home. The main problem with them is that so many Italian men are opting for the comfortable life their mothers provide instead of leaving home to marry, that the birth rates are declining in Italy.
In Germany they are known as Nesthocker (German for an altrical bird or rodent), who are still living at Hotel Mama.
In Latin America the term adultocentes is used to refer to adults who still depend on their parents as if they were children.
The Peter Pan syndrome was popularized by the movie Failure to Launch, a 2006 American romantic comedy film. It is a loose remake of the French film Tanguy, being solely based on its premise, the overgrown thirty-something child who does not want to leave home. Matthew McConaughey and Sarah Jessica Parker play the leading roles.