"Adventure Time" is such a fantastic example of that blend of whimsy and deep themes! You really see how it evolves over the seasons, especially with characters like Finn and Jake dealing with loss and personal growth. If you haven't checked it out yet, I'd recommend "BoJack Horseman." It's got that same mix of humor and heavy topics, tackling mental health, addiction, and the complexities of fame in a really raw way.
Another gem is "Steven Universe," which beautifully explores identity, relationships, and emotional healing through its characters and story arcs. Plus, the music is incredible! What other shows have caught your eye that you might want to explore next?