Possible Clues:

• "This doesn't seem right," or what can be said about 17-, 23-, 46-, and 57-Across
• 'Hmmmmm ...' [as hinted at by the three groups of black squares in the middle of the grid]
• "That's weird!" (or a comment about what's hidden in 18-, 24-, 46- and 57-Across)
• Rat smeller's words
• "Hmmm ..."