What are the drawings called that when you turn it upside down its a different o

Question: What are the drawings called that when you turn it upside down its a different one!?
Best Answer - Chosen by Asker:

it's called optical illusion, it's when u think that that's wat it is then when u turn it other way u see a different picture!.!.!. samples of these are the picture: "an old woman or a young woman!?" and "is it a rabbit or a goose!?" it doesnt need to be turn upside down though some of it can be the same position but u need to vary the spot ur looking at to see the two pictures!.!. its main mission is to trick the viewers eyesWww@QuestionHome@Com

I don't think there is a name for them because the are so obscure!.!.!. sorryWww@QuestionHome@Com