If this were any other studio, it would be a safe bet that the teaser they release will be for, well, something they’re trying to tease. However, this is Adult Swim we’re talking about, which seems to think that April 1 is 365 days per year, so nothing is certain with that company.
In fact, we don’t even know for certain that the 82-year-old Christopher Lloyd is playing Rick in the teaser, although it certainly looks and sounds like him. We think it’s more likely that they got the actor than them using his likeness through CGI or makeup, but again, we don’t trust Adult Swim at all. They could have his name in the credits and we’d still be raising an eyebrow.
The actor for Morty is almost certainly not Fox, however, as even he is nearing 60 years old. Instead, they got an actor closer to Morty’s typical age of around 14 years, which many people in the comments say looks a lot like actor Jaeden Martell.