if you brew potions wrong and drink em', you could have some spacy effects or damage. Especially if you use the wrong kind of mushrooms the spacy effect should be there <img src="/ubbthreads/images/graemlins/silly.gif" alt="" /> .
No seriously i think this would be cool <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
EDIT: perhaps you will see strange monsters, too and when you attack em they dissapear or are a rock instead and will make your sword less good if ya strike em <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> . Of course this would only be in certain potions wich have ingredients wich are not only, for example: bread, honey and water.
And of course, the less experienced alchemists could sell them to you too!
Wooh <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> the more i think of it the more cool it would be <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" /> <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />