Continuous Batting Order
Everyone on the roster bats, whether or not they play the field.
How it actually works. Standard in Little League regular season play and common in younger travel divisions. Defensive substitutions become free, because the batting order is unaffected by them.
Why it is done, and when it is wrong. It changes how a game is coached more than people expect: there is no hiding a weak bat, and the ninth through twelfth spots in the order decide a lot of youth games.
Batter's Eye: look up anything in baseball