I heard of a very powerful spell that can change a person into a vampire, werewolf, mermaid, fairy etc. for at least a few hours. I have even heard it may help one to summon a puppy and it is very easy.
The creature spell
First: write the spell for the creature you want to turn into
Second: get out candles, runes, and anything else you want to use to help focus your attention and energy on your intent. You will also need a mirror.
Third: have ready something that will help you Hallucinate. Some people use herbs while others use LSD or mushrooms. Remember to take care using LSD as it is absorbed into the system quickly.
*please remember LDS and Mushrooms are illegal therefore I cant condone using them even though people have been able to use them in the past for successful hallucination. I heard marigold seeds can cause one to hallucinate and are legal so I would suggest that.
Fourth: take everything and cast your circle and set everything up. Call your quarters, call your deity(s) perform your regular start up.
5th take the hallucinogen.
6th burn your desire in the flame of one of the candles.
7th sit and meditate concentrating on your goal for about 12-20 minutes. When you feel you have transformed, lift the mirror and see the new you.
*disclaimer, This spell is not recommended for those knew to magick, those experienced in Magick, those seeking a higher spiritual path, those that suffer from mental illnesses (including drug addiction) those that dont suffer from mental illnesses, those that have intelligence, those that dont have intelligence and or any other part of the population I have missed. Oh, and this spell should be used by no one!