Kidult

The portmanteau coinages kidult,rejuvenile,adultescent refer to adults with interests traditionally seen as suitable for children.

It can also have other meanings, such as a parent who enjoys being a parent due to spending quality time with their children, but is reluctant to lay down the law or handle the more serious aspects of parenthood. An example is Robin Williams' character in Mrs. Doubtfire, a father who has fun with his children but is a poor disciplinarian and is seen by his wife as an irresponsible head of the household.

In the past, psychology recognized the concept of puer aeternus, or "eternal boy". Today, often called "Peter Pan syndrome", it means a person remaining emotionally at that of a teenager. It is derived from the traditional archetypal "eternal boy", Peter Pan.

One of the most well-known and extreme cases of Peter Pan syndrome and the kidult mentality is Michael Jackson. Michael explicitly stated that he did not want to grow up and he owned an impressive collection of arcade video games, toy cars and fantasy and sci-fi memorabilia.

In the early 21st century, there was reporting that for an adult to have interests traditionally expected only from children is not necessary an anomaly. The entertainment industry was quick to recognize the trend, and introduced a special category, "kidult", of things marketable for kids and adults alike. Enormous successes of films such as Shrek and Harry Potter, of books traditionally targeted for teenagers and the fact that Disneyland is among the world's top adult (without kids) vacation destinations seem to indicate that "kidulthood" is a rather mainstream phenomenon. And unlike puer aeternus, "rejuveniles" successfully marry adult responsibilities with non-adult interests. When Christopher Noxon appeared on The Colbert Report on June 29, 2006, he remarked that "There's a big difference between childish and childlike".

...
Wikipedia