A plausible situation is if Johnny comes in as a relief pitcher WITH MEN ON BASE.
Johnny then commits 21 consecutive illegal pitches of the kind where he starts a pitching motion then stops. This adds a ball to the count, and the IP is assessed against the pitch count.
Of course this should never happen because the umpire is supposed to tell the DM that such a move cannot be used (ostensibly for an IBB), and by about the 4th IP, one or both of them would have been ejected. But that's another story.
"A" for effort Mike, but not the answer
In fact, in my "tease" scenario it's possible to happen even without the subject pitcher physically taking the mound--and more likely it would.
After approximately 24 hours since posting the question, and over 100 views, time to put the OP question/answer to bed.
I really thought one or more of the LL "vets" on this board would of nailed the answer from the get-go.....because the answer is in print in the LL 2012 publication "Make The Right Call.".....Nothing new, also appeared in prior years editions of "MTRC."
In case some (here) don't have the subject MTRC publication-----h/w referencing Rule 3.05----on page 21, "MTRC.."
(My note: Some quoted verbiage (below) being redundant here)
Quote: "Starting pitchers and relief (substitute) pitchers must pitch to at least one batter.
Play 3-2: Lineups are given to the umpire-in-chief at home plate. Visiting team manager, sensing an easy victory, decides to pitch his second best pitcher instead of his ace."
"Ruling: His ace must pitch to at least one batter. As umpire-in-chief, do not permit the manager to make the change until the first batter is put out, reaches first base, or the side is retired. IF it is DETECTED LATER, charge ace with 21 PITCHES pitched and REQUIRE one calendar day of rest.."
End quotes----caps mine!
Ace pitcher never having thrown a pitch to a batter in the game----is now charged with having thrown 21.
Of course, if the pitcher is 15-18 (Seniors / Big League), 21 pitches would not result in a days rest being required !!!
Don't surmise, from Lou's observation, -- that Seniors play is completely exempt from the 21 & 1 penalty. Given that league age 13's are newly allowed to be rostered on Seniors; along with previously allowed 14's---- if either age is named as a starting pitcher in Seniors play, and involved in the subject (violation) scenario, as described on page 21 of the 2012 "MTRC"--- the 21 & 1 would still appy. The key being a pitcher's age, not the division of play.
The situation/violation -(albeit rarely happening)-detected belatedly, not being confined to league ages below 14.
It would follow --IMO---LL, Inc., Should cover/cite all league ages above 14's---by noting a penalty that raises the penalty pitch count to 31 and assessing (1) days rest for those upper league ages. Particularly for those divisions, above Majors, where double headers are allowed---and a named starting pitcher, caught up in a subject violation in the 1st game, slated to start the 2nd game-----would not be allowed to pitch at all in the 2nd game.
Basically, it's the (1) days rest assessed for an Ace pitcher, that will cause a "devious" manager some "angst."