LORD SIR ANDREW LLOYD WEBBERZ'S "CATZES"
IN-WORLD: "Jellicle," as far as I can tell from what little canon there is, is more of a clan name than an actual species or power or nature. It seems to refer to the specific clan of stray London(?) cats led by Old Deuteronomy.
OUT-WORLD: It's a contraction of "dear little cats," as contrasted with "pollicle ('poor little') dogs," from TS Eliot's early poetry and letters to his young relatives.
COMEDY: "So, you know what a 'jellied eel' is, right? Well, jellied creatures were very popular in Victorian London, and it turns out that if you try to jelly a cat and FAIL..."
BONUS: ACTUAL REAL* PICTURE OF LORD SIR ANDREW LLOYD WEBBER