Fly?!
Good gosh,even rappers don't say that anymore! LOL! :D
Louise,yeah..."the cat's meow" is an old expression of the 1930's maybe 40s & yes,it means someone or something is the greatest.
Similar to that is the 20's/30's expression,"You're the bee's knees"!! LOL! x 2! I'll never understand that one! :D
Still,better than saying,"Gettin' Jiggy With It"! :D