Man Child/Playing With

Basic Trope: An adult character who acts like an exuberant little kid.

Straight: Bob is in his late 20s, yet still acts like an 8-year-old. He plays with toys and he loves candy.
Exaggerated: Bob still does everything he did as a young child - even though he's in his late 50s.
Downplayed: Even though Bob has some childlike interests, he acts adult-like in situations where it's important.
Justified: Bob didn't have much of a childhood, and is reliving it in his adult years.
- Alternatively, Bob has grown up around very immature people.
- Or, Bob is a character in a Work Com set at a toy store, and he believes playing with the toys makes him a better worker.
- Or Bob was in a coma at the age of 10 to 20.
- Another option: Bob recognizes that "grown-up" society isn't nearly as mature as it makes itself out to be, so he decides he'll just enjoy himself with his toy soldiers and not worry about being seen as childish by the guys that ask their leaders to send real-life soldiers to their deaths for some stupid, childish reason.
- Growing older is mandatory, growing UP is optional.
Inverted: Bob is an 8-year-old who wears a suit and tie every day in an attempt to look like a grown-up.
Subverted: Bob starts acting his age.
Double Subverted: He was only acting like that for a job interview.
Parodied: Bob even dresses like an 8-year-old.
Deconstructed: Bob's attempts to relive his childhood indicate some serious psychological problems on his behalf. He's never able to mentally "grow up" and remains distrusted by both adults and children alike.
Reconstructed: Even though Bob is trying to relive his childhood, he still knows when to act like an adult, so there are no problems.
- Growing older is mandatory, but growing UP is optional, and people still manage to accept him for who he is.
Zig Zagged: Bob starts acting his age. But that was just for a job interview. But even after he gets the job, he starts acting more mature.
Averted: Bob acts his age the whole time.
Enforced: "We need a grownup who acts like a little kid. This is a comedy show, after all."
- An Aesop describing how growing up is optional, whereas growing older is mandatory.
Lampshaded: "How old are you?" "Physically 28, psychologically 8."
Invoked: Bob is thinking back to his childhood and remembers how unpleasant it was. Then he gets some ideas...
Defied: Bob decides that even though his childhood was unhappy, he'll just work harder to have a pleasant adult life.
Discussed: "I don't want him around our children. He's giving them the wrong idea...in more ways than one."
Conversed: "Oh, geez, another adult who keeps acting like a kid. Oldest trick in the book."

Oh boy, oh boy, oh boy! I can't wait to go back to Man Child!