What would you do if a stranger asked you to try to move a hammer sitting on the ground after telling you it was Thor's hammer, Mjolnir? Would you be able to resist the urge to try? You'd obviously have to give it a go. How hard could it be, right?
Quite hard, as it turns out.
As cool as that was, I feel like he missed an even greater prank opportunity by simply putting it down and walking away. Imagine how funny it would have been if he waited in the wings dressed as Thor, ready to snatch the hammer right out of their weak hands.