Natasha Allegri Comics by AdventureTime-Comix, journal
Natasha Allegri Comics
I found these comics about Fionna and Cake on the AT wiki. They're by none other than Natasha Allegri.
http://images4.wikia.nocookie.net/__cb20110619205948/adventuretimewithfinnandjake/images/1/11/Fiona_and_cake.jpg
http://images1.wikia.nocookie.net/__cb20110511024506/adventuretimewithfinnandjake/images/f/f8/Tumblr_l6n17xhhfo1qzrbk9o1_500.jpg
http://images3.wikia.nocookie.net/__cb20110618031412/adventuretimewithfinnandjake/images/1/19/Tumblr_lmyfj7adyy1qzlgkno1_1280.jpg