A kid I know made a necklace with all different plastic beads, different shapes and colors. I had to put it away because it was too inviting to "fiddle" with. It became the ultimate stim toy. Some objects are like that. I'm not much for stimming but some stuff has to be touched. Every bead different, felt different looked different. And if you stretched the string you could spin beads separately, LOL.

And yea, I have aspergers so...

As for being immature altogether, not so much.