Adventure Time is good if you like the mix of comedy and, well, adventure that Gravity Falls has. Bob's Burgers has a similar sense of humor. Also, Kristen Schaal voice acts a main character in GF and BB. read more
If you like the supernatural aspect of Gravity Falls, this is a good show to check out. Rick and Morty = Created by Alex Hirsch's best friend, Rick and Morty is an even better cartoon than Gravity Falls. read more