The phrase "the cat’s crack", meaning "the height of excellence", was first coined in jest during a family conversation about the low-riding waistline of
one family members pants, Catherine(a.k.a- Cat) in Northern New
Jersey on April 15, 2018. It can be used interchangeably with the phrase “the
bee’s knees” that first became popular in the U.S. in the 1920s, along with "the cat's whiskers" (possibly from the use of these in radio
crystal sets), "the cat's pajamas" (pajamas were still new enough to be daring), and similar phrases that didn't endure: "the eel's ankle", ...