What is an immaculate inning? It is only the most dominant act that one can do in sport. Nine pitches, 3 batters, 3 strike outs. It is completely equivalent to the batters not even being in the batter's box. As shown by rule 6.02(c):
(c) If the batter refuses to take his position in the batter’s box during his time at bat, the umpire shall call a strike on the batter.
This hints at the idea of the Immaculate Game, which would be 81 pitches, 27 batters, 27 K's which is completely unthinkable, but would be stastically identical to a team of 9 toddlers trying to bat. A list of all pitchers who have thrown an immaculate inning can be found here.