A crossover between Steven Universe and Super Giant Robot Brothers would be so funny because it just fits. Literally nobody outside of Beach City seems to know anything about the Gems, despite how much they screwed with the earth, and Beach City, despite having plenty of out-of-town visitors every summer, seems extremely disconnected from places outside of their town and they’re extremely used to weird alien junk happening. Three giant aliens who were tyrannical rulers mere moments before they went to earth showed up when there was a concert and everyone was just kinda like “oh hey Steven’s home.” Because of that, they wouldn’t really NOTICE anything to do with the kaijus and all that, Homeworld Gems were busy fixing their society and everyone on earth was just trying to chill out and finally live their lives in peace.
Neither knows the other exists, but at some point the base would pick up the Gems because they’re going to earth and hanging around it more, and I think that’d be a very silly interaction because none of the Gems understand what they’re talking about. “Kaijus??? Like those monsters from the movies??? We’ve heard of them.” “What do you mean there was a wormhole above earth? Oh, okay we were kind of busy with an intergalactic war around then. Thats why we didn’t notice.” “You know when the entirety of earth was enveloped in pink goo and everything almost died, then it was back to normal in about a week? Yeah, sorry, that was one of us.”