This is a "brainrot" phrase/word like skibidi, alpha, rizz, etc. It simply refers to aliens, the color green in general, something being cute or adorable, or more rarely semen. It overall has no negative connotation. It is sometimes also accompanied by being said in a goofy voice, but can also be said without. The most common sentence using it is "what do you know 'bout that goo goo green?"
by Internet Cupid March 13, 2025