Casper starts making that weird sound cats make when they're hunting something (chattering - and yes, I know, YOUR CAT DOES THAT TOO) while chasing a laser.
He has not had any catnip - this is just how he acts normally.
We did not shine the laser in his eyes (that would be moronic), and since it has disappeared in the house somewhere, he can no longer hunt it.
P.S. For those who asked: he may be half Maine Coon, but we aren't sure. His mother is a calico.