When throwing killerducks if you throw them all very fast while looking down a bit they will stack on each other and all get stuck in 1 place until they explode. When you look at the screenshot they look like there moving but they were 100% stuck XD. Also sometimes killerducks get stuck on each other when travelling when they bump into each other. ~Psychic Pad
Added from old bug tracker and affects WoP 1.6.
When throwing killerducks if you throw them all very fast while looking down a bit they will stack on each other and all get stuck in 1 place until they explode. When you look at the screenshot they look like there moving but they were 100% stuck XD. Also sometimes killerducks get stuck on each other when travelling when they bump into each other. ~Psychic Pad