As I typed the final F in [ELFELF] at 25Across a moment ago, I found myself saying out loud, "now isn't that interesting." Only when I had completed the entire puzzle did I figure out the trick. It's a lucky thing for this solver that a good number of the Downs were gettable, so there was little question in my mind that I had at least most of the theme answers completed correctly, which was comforting because OMAN OMAN, they sure looked funny. While the clues were pretty straightforward, in order to correctly parse the answers the solver must render the doubled words in the shaded squares into their respective plural forms. So, to get a recognizable answer to "Program followed in Alcoholics Anonymous" one has to read TW[ELFELF]TEPS as TW[ELVES]TEPS. The other necessary changes are DIEDIE to DICE for COME[DICE]FFECT, MANMAN to MEN for NA[MEN]AMES (which, by the way, had the great clue "Sing under pressure"), and finally, the amusing FOOTFOOT to FEET for COF[FEET]ABLE. I think I can safely BETCHA that I wouldn't have come up with this crafty idea in a million years.
With some trick puzzles, the rest of the grid suffers, but I don't find that to be the case here. There was a lot to enjoy from "Oak in a nutshell" (ACORN) and "Got into the swing" (SAT) - really good one! - and "Change in the Middle East, say" (DINAR), to the excellent "What a swish misses" (RIM) and my favorite, "Razor handle?" (OCCAM) - ha! I also noticed that if you read 34A and 35A together you get SLOE MOE. :)
In sum, this review found nary a thing to POOH POOH. High [FIEFFIEF] all around!