Whatever I feel like

I’m still working on that.  I just thought of a great side effect, and wanted to put it down first.

Side effect: the people who speak that tongue natively will NEVER be able to understand you, no matter what language you speak.

Side effect: you become 10 times slower and 10 times weaker, causing you to work even harder just to match the strength of your enemy

Side effect: you will show symptoms for whatever ailment you cure for the next 24 hours

Side Effect: They are anatomically incorrect (although they look sick) and can't actually be used to properly fly.

Side Effect: You're stuck looking through their eyes for at least an hour

Side Effect: you loose your ability to communicate with people. You can only use sounds of that animal to communicate/cannot mimick human speech.

Side effect: You gain the difference in weight.

Side effect: Shapeshifting is apparently really loud, similar to the sound of popping bubble wrap. The more of yourself you change, the lounder/more popping goes off, easily drawing more attention to you than you might like.

Side effect: They hate you for taking them from their home

Side effect: your heels break at the end of the day so you must buy new ones all the time

Side effect: They subsequently try to kill you