If you haven't seen the show, here are a couple of pictures for reference:
Prince Gumball
Jake the dog, Princess Bubblegum, and Finn the human
Lumpy Space Princess
Pumpkin Pie made this picture of her favorite characters:
And then she made some fan-fiction with Prince Gumball and Princess Bubblegum hooking up, and having a baby! And get this, she named her princess Jelly Bean.
It kills me how creative she is. She can just sit down and bang out a drawing like this without having any pictures or reference points besides her mind's eye.