My son has ADHD. He is distracted by anything shiny, or soft, or cats. He is delighted by many seemingly insignificant things. Over the weekend my family went to Jack in the Box. Michael was enchanted with the fact that they had new straws at Jack in the Box. Oh, and a crow that was outside on the grass.
Randy said, "I wish I had ADHD, so the world was constantly full of wonder."
We also had a talk about how many of the best and most interesting characters have ADHD. Steve Irwin. (Would he have gotten his own show, if he didn't have ADHD?). Ty Pennington. Doctor Who. Many of the most interesting characters in various books. Plucky sidekicks in many situations.
I think we love grownups with ADHD because they are so out there. When they're excited, they share that enthusiasim with everyone. They don't hold back, or think "I'm an adult, I should be calmer about this". They jump in without looking, think outside the box, and remind us of how wonderful things can be. On the down side, they share their enthusiasim with everyone, they don't hold back, they don't think "I'm an adult", and they jump in without looking. This can cause delightfully sticky situations for your characters.
Do you have a character that could benefit from a little (or a lot) of ADHD?