Gravity Falls references in the Simpsons:
In the episode „Homer and her sisters“ from season 36, you can see a small gravity falls reference behind the simpsons family. It appears to be a children’s dentist office named cavity falls which seems to be a direct hint at gravity falls. Maybe it was named after Springfield‘s possibly neighboring town gravity falls?
Also not to forget the cameo of bill cipher appearing in a vision/hallucination the simpsons family has, in which he tells them to go buy crypto.
Interestingly, this is the only time, alex hirsch did a voice over for a bill cipher cameo in another show. Most obvious explanation is of course that hes a huge fan of the simpsons and thats why he did it but the theorist in me likes to believe that this just proves that bill cipher is actually real and is in the dreams of the springfieldians, alongside jesus apparently.
He also made an appearance in one of the simpsons‘ intro segments a few episodes later.