You stumble across a lamp with a Genie. He only grants one type of wish (with rules).
You get to be turned into an animal of your choice for a duration of between 20 minutes to one day. The duration is also your choice.
You will be transported to a location of your choice for this duration. You can interact with the world there.
You are not allowed to intentionally physically harm humans.
If you die in that location, your time is up and you reappear back here unharmed.
Mine is unimaginative. I would want to be a huge lion in a crowded square in London. Chasing around screaming people (adults only) would be so much fun. I would jump on top of cars and roar.
In the US, all cops have guns and I would probably be shot with too many bullets in short order. In the UK it would take longer.