One cut/trim that really wasn't merited was the "She Loves to Hear the Music" number in THE BOY FROM OZ.
In early previews the number was quite long then later trimmed/chopped to what ended-up in the show. Ugh!
Originally, Stephanie J. Block (as Liza Minnelli), began the number as a rehearsal with her sporting a chunky rehearsal-type sweater with the dancers all sporting 1970's dance rehearsal gear (leg warmers, et al). After the first verse, Stephanie disappeared while the dancers went into a whole 1970's A CHORUS LINE meets Bob Fosse-esque dance (including a great Fosse 'amoeba' moment), which helped build momentum to the number. As the number was building, ALL of the dancers darted off the stage and the slow black reveal opened to the HUGE enormous red neon LIZA sign with Liza now in her famous LIZA WITH A Z red sequined mini-skirt. This reveal was explosive since it came as the music was building up to that moment. Then the dancers came on (now dressed in those Fosse-esque black suits with the white ruffles, etc.) and they did the number as the LIZA WITH A Z-esque number we all remember.
That entire opening was modified completely. The number ended-up with Stephanie beginning the number already in the red LIZA WITH A Z mini-skirt, so that killed any excitement. Gone entirely was that entire A CHORUS LINE meets Bob Fosse section and all that remained was just the LIZA WITH A Z-esque dance number.
I should post that original full number on YouTube.com so others can see it since only a few preview audience members got to. It was slaughtered quickly.