Unknown Ponies: Zebra Alchemy

Zebras are just Ponies from a faraway land. While they look exotic and have unusual methods of speaking (usually in rhyme), they are functionally no different from other Earth Ponies. They do however have one skill unique to their people: Alchemy, the study of potions both magical and mundane.

Alchemy is a Mind skill which only Zebras may possess during character generation. However, anypony may learn to use it, provided they have a teacher.

Just like any sort of magic, Alchemy comes with its own strange set of rules. Take it away, Zecora!

So you wish to have a notion
How to mix up zebra potion?

Gathering up potion ingredients
Is never simple nor expedient.

Your potion only affects life;
Not rock, nor dirt, nor carving knife.

If you meddle in ponies' feelings,
You do not know with what you're dealing!

When Ponymaster hears your song
She might just say "It's much too strong."

As you describe your potion's effect
Every rhyme you must not neglect!

So you must be the potion's master
Or careless rhyme will cause disaster.


Slightly Crunchier Rules
The rules for potions are actually pretty simple:

1. Decide what the potion will do. As stated above, it only affects living things. The best way to describe its abilities is to say that alchemy cannot change a thing's nature: if it was a pony when it started, then you can't change into a non-pony. However, you can take what a pony is and take that, for good or for ill, further than it could naturally go on its own. As a curse-breaker, alchemy can look at a thing's true nature and change that thing back into what it was. 
2. Based on this description, the PM decides whether this potion is Minor, Significant, or Major. Minor potions are just that: perhaps they change the color of a pony's mane, or create fireworks, or soothe a sore throat. Significant potions are more powerful, transformative or curative in nature. (Most of Zecora's potions within the show are Significant.) Major potions are just that: if it makes the PM say "Whoah," then it's likely Major. 
3. The ponies must gather ingredients. For Minor potions, it's as simple as going to the market, or perhaps rooting around in a garden -- something which can be accomplished quickly and easily. Significant potions are much rarer, and require a side-quest or mini-adventure to achieve -- perhaps a rare herb that grows in only one corner of the Everfree Forest. This should take approximately one Act to complete. (Example: the "Love Poison" from Hearts and Hooves Day.) Major potions are the stuff of legend, and require a quest just to themselves to complete. 
4. Make a rhyming couplet that describes what the potion does. Yes, it has to rhyme -- and scan.. If it doesn't, the potion will fail. The exact results are up to the Ponymaster, but a slight mis-rhyme (such as "orange" and "porridge") will likely only have small or cosmetic side-effects. However, terrible rhymes, broken meter, or attitude such as "I don't want to make a stupid rhyme, just let me roll the dice" will result in hilarious, epic failure of the sort that would make even the Cutie Mark Crusaders look highly competent. 
5. Now it's time to roll. Don't fail. Consider spending a Magic point.
6. The Ponymaster now considers is then free to twist the wording like a Genie's wish. Naturally, the more carefully worded the rhyme, or the better the roll, the more likely it is to work. Also, more moderate wishes ("I want nice hair") are much more likely to succeed than greedy or outlandish ones ("I want to have pegasus wings and a unicorn horn!"). Take full advantage of unintended consequences, especially if the potion changes free will or emotional states.
7. Watch as hijinks ensue.