Opal

if reject dolly is the one who turns plushies into rejects, then we can assume tis through the same way dolly nearly did in Inspection Day!! their powers seem to be based on their emotions; when dolly gets stressed, bad things happen to plushies around her! reject dolly could be taking advantage of this and misusing her/their power, b/c it seems she was supposed to use it for good like dolly does, but is instead using it to create rejects!..

another big theory related to this is that the bosses are the only reject version of their plushie!! every other plushie haz multiple rejects of themselves, but the bosses seem to only get one, and a unique one at that!!

(reject jellybell possibly being a literal cautionary tale for the plushie jellybells and tritons v)

(jinx referring to reject meistro as if there's only one of him v)

(we can assume that reject koda is also the only one of his kind!!)

another scary thing is that there is apparently only one reject shrubi, but unlike the bosses (reject shrubi is a mini-boss), they became a reject through too much experimentation, possibly while looking for a cure for the rejects..

(reject shrubi's desc in-game ^)

so, the reject bosses and reject shrubi had a possibly more unique way of becoming a reject compared to the other rejects!!

but these are only theories!! again, nothing's been explained/confirmed in canon!! so, feel free to come up with your own theories about this, and ask more questions!! :D

sometimes her confidence makes her an easy victim to jokes, tho!! not b/c she was asking for it; tis moreso the pranksters knowing she can withstand it, and also, her knowing this takes their attention away from other targets!! (this is...MY interpretation; you can interpret it however you wish!!)

there's one in-game dialogue exchange that sort of shows her deserving it, tho!! :P but genuinely this could be a compliment from both of them, in a way!!

queenie flatters others, not just herself!! (similar to meistro as i've said!!)

also, she's into fashion!! she cares about appearances, but i wouldnt say she's truly vain!!

she's more careful and patient than you'd think; queenie is both a gardener and baker!! she frequently grows things to use in her baking!! and her favorite thing to bake is cake!!

she and jellybell are rivals, but friendly ones!! tis implied queenie is usually the one who starts their quarrels, but tis not something done out of malice!! perhaps tis an effort to keep jellybell at her best!! :P

and queenie's favorite music is from CONSTELL3 (the fictional artist of Mango Mochi, one of hi-fly's in-game songs)!! she's not so pompous to hold back from her favorite activities, which truly makes her seem confident!!

feel free to come up with headcanons and theories about queenie, and keep asking questions!! :D