Holy cow, that's totally fiction.
Wicca isn't about spells... it's not about imaginary things like polymorphing.
Wicca is a religion-- it's about how we worship our Gods, and how we live our lives.
A big tenet of Wicca is observing nature... notice, in nature, you cannot alter the laws of physics.
This idea that Wicca (or Witchcraft, for that matter) has anything to do with transforming your physical appearance by muttering a few rhymes comes from fiction.
You can find all kinds of crazy crap on the internet, but hon, if you ever went to a big Wiccan gathering and asked people about that, you'd be laughed out of the place. That's not even something we consider as part of our religion, not even a little bit.
I'm not saying that to be mean-- I'm saying that to explain just how absurd the very idea would be.
It'd be like walking into a church and asking seriously if praying to God could make you a superhero who flies.
It's along those lines. It's one of those things that have Wiccans shaking heads wondering "where the heck to people get these ideas about our religion? Charmed?"