This is a good first mission. It showed off both agents' personalities in contrast with each other, and made use of their species' physical characteristics. (I'm amused to see an agent pair that both have to disguise themselves as humans in order to blend in on a mission!) I particularly like Agent Charlie, with their laid-back reactions of "cool" to stuff that most agents would be annoyed by.
A couple of suggestions: Not being familiar with Plants vs. Zombies, I wasn't sure what a "Chomper" was throughout most of the mission. I was thinking it was a zombie, since zombies are known for chomping, but then you named it as part of the plant faction near the end. I would advise either describing it a bit, or just stating that it's a plant early on. Also, since a lot of folks are offended by the term neurodivergent slur, I would warn in the opening notes that it's being quoted in the mission.
And a few mistakes:
"Jiwon lifted a leg out of the glitter river to look at his shoe. 'Do you think these will come off when we drop disguises?'”
"Uncountable" nouns like liquid get referred to with "this" instead of "these."
"Pulling a waterskin out from their bag, Charlie drank deeply, washing down the stomach acid in their mouth."
I may just be speaking for myself here, but I think most people would swish the water around their mouth and spit out the acid, rather than drink it back down.
And lastly, there are two sentences where Jiwon got Charlie's gender-neutral pronoun instead of his own:
"Jiwon blanched and ran a good distance back down the corridor, away from the smell. Charlie glanced down after them . . ."
“'It’s fine,' Jiwon grunted, rolling onto their back."
—doctorlit found it disorienting to read about a sunflower character who wasn't the Official