Age-Nonconforming
Not adhering to traditional or cultural expectations of their age. An adult who is age-nonconforming may enjoy children's media, dolls, or participating in childish activities. A child who is age-nonconforming may like more mature media or dislike children's media or participate in mature activities. Age-nonconforming may also take the formal of childish or mature attire.
I may be an adult but I like kids' shows and acting childishly. I am age-nonconforming.