Gem Language Theory
So I’ve had this theory kicking around for a while now - the idea that this isn’t just a ‘cartoon world’ where all the characters speak the same language and we’re just meant to suspend our disbelief. I think there’s actually a gem language. In the show so far I’ve seen two pieces of evidence supporting this. One was when Centi revealed that there’s a gem writing system. The second bit of evidence I’m going to take from the new leaks (minor spoilers) where Steven is speaking in the presence of a homeworld gem who has never been to Earth, and she doesn’t seem to understand him at all. Calls it “barking” I think.
So I theorise that there’s a gem language, but in order to support this theory I need to believe a few things. One - that Steven and Greg both speak gem language. Two - that gems are very fast learners and can pick up English quite quickly if they try.
Steven can understand the Crystal Gems (because they would have learned English, of course) but then Steven shouldn’t be able to understand homeworld gems (such as Jasper, Peridot, Yellow Diamond, or other gems we just saw in the leak.) Yet Steven can, even though these gems shouldn’t be able to speak English. So therefore, Steven can understand 'gem.’ This was probably taught to him by the Crystal Gems. (Although they apparently neglected to teach him the written language.) He also could have been taught by Greg.
Greg, I think, must also understand 'gem’ because he too has been in the presence of homeworld gems (who should not be speaking English) and yet has understood them. Such as that time with Peridot when she pushed him off the barn, or that transmission from Lapis warning everybody that homeworld was coming. (As well as stuff from the leak, of course.) I suspect Rose made an effort to teach Greg how to speak 'gem’ or if she didn’t then certainly Steven would have by now. But I like to think that Greg has been speaking 'gem’ sinve before Steve was born, because I think Steven isn’t really aware that he speaks two languages. Like, it hasn’t really registered with him, because it’s just always been this way. (And I could imagine an adorable episode later with Connie, where he sees that maybe she speaks a different language at home and he thinks that’s so cool, but then Connie tells him 'well, don’t you also?’)
Lapis and Peridot are later seen talking to humans (like Mr. Smiley or Uncle Andy) therefore Lapis and Peridot must have picked up English at some point. We know Lapis as a mirror was taken all around Beach City by Steven for a day of learning to repeat words. We also know that Peridot sat through all those episodes of Camp Pining Hearts and memorised the lines, repeating them back to the TV. So I theorise that gems can pick up languages very fast, and that this is how Lapis and Peridot learned to speak English. (Has Jasper learned English? I’m not sure…)
(Leak info again - the people with the earrings all speak gem, that’s how they understand the little voice and also each other, and how Greg and Steven can understand them, because it would be silly if they were all speaking English.)
Anyway, that’s the theory, and I look forward to future developments.