I'll go ahead and answer this for the rest of my OCs, since I only did Willow yesterday.
What would happen to your pony(ies) if they ran through a patch of poison joke?
Catnip:
Gets a dog snout and her speech is randomly interrupted by unintentional barking. It would scare her kitties, mostly, and would be generally inconvenient.
Mystery:
Would start shifting randomly and be unable to control her changeling abilities at all. This could range from accidentally being pink all of the sudden to shifting to look like Princess Celestia.
Willow (Already stated hers, but it's funny so I'll repeat it):
Her magic would get blocked up, and then release a wave of it whenever she sneezes. She would also have an itchy nose until the poison joke wears off.
Indigo:
Would probably be shaking until it wore off, thus rendering it almost impossible to do anything that would require precise action.
Downy:
Would probably molt all of her wing feathers, so she couldn't fly and would just have unappealing wing-nub things on her back.
Story:
Her voice would be cracking and changing pitch while she tried to talk, making her sound something like a broken record. She wouldn't be able to effectively sing or tell stories if she couldn't talk right.
Silent:
Wouldn't be able to talk quieter than a shout. She doesn't like being the center of attention, and not being able to say anything without everypony nearby hearing would be a difficulty for her.
Moon Jelly:
Her legs would become elastic-y. As much as she loves jellyfish, she wouldn't want her legs to feel like them.\
Two:
Her head would grow to about three times its normal size, so that she had to lie down in order to keep from toppling over.
Bobtail:
Her mane and tail would grow out super long and bushy, and she would constantly trip over them.
Dirty Paws:
She would get giant hooves, which would make it pretty much impossible to take anything without being noticed.
Evening Star:
Are angel ponies affected by poison joke? I'm not really sure. She would probably get literally tongue-tied whenever she tried to say something sarcastic or witty.
What would happen to your pony(ies) if they ran through a patch of poison joke?
Catnip:
Gets a dog snout and her speech is randomly interrupted by unintentional barking. It would scare her kitties, mostly, and would be generally inconvenient.
Mystery:
Would start shifting randomly and be unable to control her changeling abilities at all. This could range from accidentally being pink all of the sudden to shifting to look like Princess Celestia.
Willow (Already stated hers, but it's funny so I'll repeat it):
Her magic would get blocked up, and then release a wave of it whenever she sneezes. She would also have an itchy nose until the poison joke wears off.
Indigo:
Would probably be shaking until it wore off, thus rendering it almost impossible to do anything that would require precise action.
Downy:
Would probably molt all of her wing feathers, so she couldn't fly and would just have unappealing wing-nub things on her back.
Story:
Her voice would be cracking and changing pitch while she tried to talk, making her sound something like a broken record. She wouldn't be able to effectively sing or tell stories if she couldn't talk right.
Silent:
Wouldn't be able to talk quieter than a shout. She doesn't like being the center of attention, and not being able to say anything without everypony nearby hearing would be a difficulty for her.
Moon Jelly:
Her legs would become elastic-y. As much as she loves jellyfish, she wouldn't want her legs to feel like them.\
Two:
Her head would grow to about three times its normal size, so that she had to lie down in order to keep from toppling over.
Bobtail:
Her mane and tail would grow out super long and bushy, and she would constantly trip over them.
Dirty Paws:
She would get giant hooves, which would make it pretty much impossible to take anything without being noticed.
Evening Star:
Are angel ponies affected by poison joke? I'm not really sure. She would probably get literally tongue-tied whenever she tried to say something sarcastic or witty.