i begin this post by asking you to examine the designs of all the gems we’ve seen so far (sans steven, a half-human) 

note one major similarity between all these gems: they have no visible ears

i realize this is only a small sampling of the gems so far seen, but i got lazy. just  trust me. none of them have ears.

now, in the return, jasper makes mention of a “yellow diamond”, obviously a higher-up on gemworld. someone who has a lot of power. this someone, could (and probably would), hypothetically, have more knowledge of earth than anyone may know—including jasper and other homeworld gems. 

my theory is as follows: we’ve already seen yellow diamond. in fact, they’ve been here all along. 

who are they, you ask? 

think to yourself. dig deep. who is it that has no regard for rules, or human life? who seems just too strong to be human? who is it that has no ears?

that’s right. yellow diamond, the series’ antagonist, is onion.