Cinnamon Bun In a Dress is the gender swapped version of Cinnamon Bun. She makes a minor appearance in "Fionna and Cake" as one of the guests at the Biennial Gumball Ball. She asks Prince Gumball "I wonder if you designed it yourself" in a very mumbled tone.
She appears for the second time in "Bad Little Boy" at Lumpy Space Prince's party in the woods. She is seen dancing with him as well, mumbling and laughing. She can be seen in the crowd watching Marshall Lee and Fionna perform.
Cinnamon Bun in Dress is similar in appearance to Cinnamon Bun except with green shoes, a dress, and a bow. The only physical differences between her and Cinnamon Bun are longer eyelashes, breasts, and white eyes, as opposed to Cinnamon Bun's black eyes.
I wonder if you designed it yourself.
Oh my Glob, I can't believe this is happening to me!