YOU SAID:

throwing that turtle on my knee

INTO JAPANESE

その亀を私の膝の上に投げつける

BACK INTO ENGLISH

Throw the turtle on my lap

INTO JAPANESE

亀を膝の上に投げる

BACK INTO ENGLISH

throw a turtle on one's lap

INTO JAPANESE

膝の上にカメを投げる

BACK INTO ENGLISH

Throw a turtle on your lap

INTO JAPANESE

あなたの膝の上にカメを投げる

BACK INTO ENGLISH

Throw a turtle on your lap