I recommend Gravity Falls. While it's a show mainly aimed for the child demographic, it has adult under tones and mysteries that genuinely leave you puzzled; and you can tell the show is well loved due to the amount of depth, preparation and hidden easter eggs throughout the show that actually uncover a bigger picture -- It's even in the same universe as the beloved show Rick and Morty, Rick and a character from the show being canon friends
"Rick and Morty" has parallel stories! Cool. Didn't know that.