Casper is one of those more predictable "laugh at the funny parts" kinda guy. Brock, on the other hand, isn't discriminating when it comes to the chortles. Any sort of physical injury, loss, or downturn in fortunes is ripe for hilarity. Certainly not anything worthy of getting him on a list or anything. If the bad guys are doing their evil laugh, something funny is happening, right? So let's laugh right along with them! Yeah. Totally appropriate in all circumstances.