Foster's had a knack for presenting a "dark" world without ever leaning too hard into drama or despair. They were able to do that because the premise of the show is lowkey a creepypasta, like, what if all your friends aren't real, and what if they regularly get abandoned? It's such a dark undertone that you just have to gently remind people of it every now and then to achieve real pathos and emotion, while the rest of the show can be whimsical and hilarious. Goo is a great example, as well as Wilt's backstory, and Mac's entire home life.