As an adult, what seemingly childish things do you get excited about?
I love bridges. If I see a cool looking bridge, I want to cross it, especially if it goes somewhere that I'm not familiar with. Same with stairs outdoors. They feel like an adventure to me.
Rainbows, shiny things, stuff that smells good, really bright colors (a lady I work with sometimes wears magenta sweaters and they make me happy), gears, bells, and flowers.
Off the top of my head, but there's probably more.