It has an animated texture thats similar to Oil & Snot and its surface bubbles when a qbee sinks in it. It may also bubble from time to time. It is similar to Oil, Lava, Quicksand and Snot and it can give Damage to Qbees who sinks within it. Once you have sunk within the block, you start gaining damaged, so do not forget to jump when you're stepping on it!
Pets can also die once they go through the block.
The block is also perfect for restricting Slymes in an area since Slymes can not pass Green Goop. They are also required to produce Slyme Splats but how one may produce it is a hidden secret -spoilers-.
How to obtain