They're White

Two african american kids, a boy and a girl, go out trick or treating and stop at a lady's house for candy.
- Who are you two supposed to be ?
- Hansel and Gretel.
- You can't be Hansel and Gretel, they're white.
So the kids went home and changed and went back to the lady's house.
- Now who are you supposed to be ?
- Jack and Jill.
- You can't be Jack and Jill, they're white.
Then the kids went home to change again but went back to the lady's house with nothing on this time.
- What are you supposed to be this time ?
- Hershey bars, one with nuts and one without.