My inner child is shy and quiet, or in other words a more extreme version of my adult self. I keep my Squirtle stuffie which I've had since I was a child with me, constantly, at my side. I'll usually watch cartoons or read (including some more mature stuff my inner child should not be reading or watching, horror gets me occasionally!
) or just play games for a bit on my Switch, usually either Smash or one of the Mother games. Or just enjoying a paci, my diaper, or any of the other joys of being little. Or, sleeping works too.
In other words, my inner child is basically a smaller version of me. I tend to stick to a lot of the things my big self does when I'm regressed.