Possible Clues:

• "Thanks, but __ already"
• ''Must be something __''
• ''. . . must be something ___''
• ''. . . __ the whole thing!''
• "___ when that 'appens!"
• '… ___ the whole thing!'
• 'Must've been something --'
• “Must’ve been something ___”
• "It must have been something ___"
• 'I can't believe ___ ...' (old ad catchphrase)