Cat

I was frustrated with the clue on St. Louis, and then shocked to read the puzzle author is from Missouri himself. I’ve neither seen nor heard of STL ever referred to as “the Lou.” I’d be embarrassed for anyone calling it that out loud. While I’m sure there is no reference work puzzle authors must cite for the veracity of their clues, this clue bothered me enough to comment. Can puzzle-makers create nicknames?

The plural of “rebus” is “rēs,” since it’s a 5th declension word. It’s 2nd declension that uses the -ī in the nominative plural.