Rottweiler Riddle

Hey, listen up, you big dummy! This isn't rocket science, even for you. The question makes you think of some weird creature, right? Four legs, one arm. But then the answer hits you: a Rottweiler (that's a big, strong dog, buddy) in a children's playground. Now, dogs have four legs, right? So, if it's got "one arm," it means it ripped off a kid's arm! Get it? It's dark, it's messed up, and it's supposed to shock you. You probably thought it was a creature from your fantasy book, didn't you? Tsk tsk.