I don't know if this bug has been reported already, so if it has, just delete the topic.
When you eat a heavy as an onos, and jump(maybe from a medium high distance, I haven't looked into if hieght matters) your footsteps make the sound like a heavy's when walking. Only makes the sound when jumping, walking is still the normal onos footsteps.
Easy to reproduce. So, Yeah. Most likely a bug like this has been reported, but sifting though your bug "engine" is really hard and I haven't seen a thread for such a thing.