IATE

Set to 9 different clues across 17 published puzzles, most often "Must've been something ___" — The New York Times, Friday, 18 March 2011.

4 letters

Every clue on record, most used first

"Must've been something ___"7 times
The New York Times — Friday, 18 March 2011
"Must be something ___"3 times
The New York Times — Tuesday, 27 September 2005
"It must've been something ___"once
The New York Times — Wednesday, 22 June 2011
"___ it up and spit it out" ("My Way" lyric)once
The New York Times — Thursday, 26 May 2011
"I can't believe ___ the whole thing!"once
The New York Times — Monday, 30 November 2009
"? ___ the whole thing!"once
The New York Times — Tuesday, 1 February 2005
"I can't believe ___ ..." (old ad catchphrase)once
The New York Times — Monday, 24 May 2004
"I can't believe ___..."once
The New York Times — Thursday, 13 August 1998
"I can't believe _____..."once
The New York Times — Saturday, 5 November 1994