I can't say any of us besides Bleat have been a cloud! But I bet it would be interesting; take a slime and somehow boil it enough to get it to evaporate, maybe after being diluted in water, and watch a dark, stormy cloud form from it. Of course, eventually, like any cloud, I'd cool enough to just sorta turn back into slime, and soon it's raining tiny slime Umbreon that will convert who or whatever they hit into more goo while it rains and before I reform proper. So probably best not to be a cloud unless I want to indiscriminately tf a huge area at once, which admittedly is exactly my flavour of evil plan when in an evil mood.