@CloudMistDragon
Very true - though I feel I should note you’re obviously speaking of MYM only, as her first appearance is in episode 5 of TYT, Mane Melody, while IIRC her first voiced appearance is in episode 7/8, Clip Trot (I forget whether it’s 7 by production order and 8 by release order, or vice-versa).
I only really bring that up, however, because I watched the first four episodes of TYT a little under a week after they were released in April 2022 (on April 13th, to be exact, right after I watched the movie for the first time), and didn’t watch episode 5 until September (the 3rd, IIRC), so when I would explore the comments section on Derpibooru, I kept thinking “who is this Posey character everyone keeps bringing up?”, haha
Speaking of episode 5, I think it’s interesting that what can essentially be considered the theme song of TYT (considering its instrumental plays over every TYT end credits sequence), in “Let Out Your Light”, doesn’t appear until then.