Solution: Turtle-shelled flunky of 1-Across - NYT Crossword

The first across entry and the most visually prominent down entry in this puzzle are related, and they are both out of my bailiwick. At 1A, the [Fire-breathing antagonist of Mario in the Mario universe] is BOWSER, which has been clued a variety of ways in the Times puzzle: as a dog’s name a few times; as the mayor of Washington, D.C.; and, in its 1956 debut, in a Eugene T. Maleska puzzle, as [Bing Crosby’s name for his toupee]. At 16D, the [Turtle-shelled flunky of 1-Across] is KOOPA TROOPA, which is a puzzle debut. (Funny enough, this is what Bing Crosby called his fleet of Continental Mark IIs. I jest, but you never know.)