The character's been around for close to 70 years. He's only been killing with gag weapons since the 70's. I wouldn't call that most of his existence.Funny that you're trying to spin this that Nolan twisted the character to make him oh so new and hardcore, when he's actually closest to the Joker that appeared in Batman #1. The only real difference (apart from superficial issues like the lack of permawhite skin) is that he didn't use Joker venom in this movie. Unless you count the grenade he used on the bank manager, but that gas could have been anything.I seem to recall him laughing his ass off when the helicopter crashed and when he threw Rachel out the window. Yes, these are only two instances, but you have to take into account that the Joker actually didn't have a whole lot of screentime. Perhaps these things don't count as "trivial" or "no reason at all", but I don't remember the modern Joker ever busting out with the HaHAhAHa's at random, either. He usually does that after he's done something horrible to somebody (like blowing them up with a trick cigar).