Grumble is basically the same concept as rawr, a random word to say at random times. But the real purpose of grumble is to start a big thing all over Kidzworld about grumbling. Get everyone to start saying Grumble! Please, start using it! Post it on your profile! Tell your friends! You can even join the grumble group!
C'mon guys, have a little fun and start a new trend c: