The sponge emoji depicts large dish (or car) sponge. It can be used to depict that you need to wash something, like your car. Or that you are so dirty you need to wash yourself with a big sponge. Most platforms depict the sponge as yellow with holes in it, and some show a green sponge. Either way, you’re getting clean! A sponge can also be used to represent the mind of child, a quick learner, or someone who can "soak up" information.