Play "Hide and Seek" and tell him to hide first and then just run away and dont look for him...... or you hide and then just apparate far away and he'll be looking for you forever.
Take out a guitar and start singing and out of nowhere hit him in the head.
Say you know where he can get the Prophecy cause someone dropped it and take him deep into some forest and then say "Wait, we're in the wrong forest." and then keep going all over the wizarding world and and keep saying we went the wrong way.