Lord Monochromicorn is the fictional gender-swapped version of Lady Rainicorn created by the Ice King in his fanfiction story, as seen in "Fionna and Cake." He is the loyal companion of Prince Gumball and the boyfriend of Cake. He communicates by using his hoof like a telegraph to communicate with Morse Code, rather than by speaking Korean, as Lady Rainicorn does. (He stomps his hoof for a dot and scratches the floor like a line for a dash.) Cake can understand him clearly.
He is completely charcoal black with a long, gray mane, with white-slit eyes. His long, white horn has two rings circling it. He is entirely different from Lady Rainicorn's multicolor scheme. He is more horse-like compared to Lady Rainicorn.
According to Natasha Allegri, he can open up black holes. He can also stretch and fly like Lady Rainicorn.
- Lord Monochromicorn neighs like a horse.
- Lord Monochromicorn was really created by original series designer Natasha Allegri.
- Lord Monochromicorn can be unlocked in Jumping Finn.
- During his first appearance in the actual show when Cake greets him with "Hiya gorgeous!", he replies "Hey," in Morse Code. In the original storyboard, near the very end of the episode when Fionna and Cake are talking about how much they love the Ice King, Lord Monochromicorn shows up and uses Morse code to say, "We Love You Ice King!" In the completed episode, Lord Monochromicorn's first statement is "Hey", and his second statement translates to "ISE?" (resembles ICE, because Fionna and Cake are talking about Ice King).
- When Lord Monochromicorn made his first appearance on screen, the sound of thunder could be heard in the background.
- In the original storyboard, Lord Monochromicorn's horn is shaped like a lightning rod, his eyes are like Lady Rainicorn's, and he spoke English instead of using Morse Code.
- Prince Gumball sometimes calls Lord Monochromicorn "Mo-Chro."
- Lady Rainicorn has said that she flies by using light and "dancing" on it. However, Lord Monochromicorn is black, which would mean he would absorb light.
- He and Lady both have small things to do with rain/weather. Lady resembles a rainbow, which happens after sunlight is refracted by rain, while thunder is heard when Lord Monochromicorn appears and his mane is gray which resembles the gray clouds that appear at storms..
- Additionally, their color schemes are the opposite of each other's; Lady has a rainbow-colored body (to go along with her powers), where as Lord Monochromicorn is black, white, and grey, which are usually used to indicate a lack of color.
- Lord Monochromicorn's name is an allusion on the words "Monochrome" and "Unicorn". Monochrome refers to a type of special painting in which the artist uses the same color, or different shades of the one color, to construct the artwork. This explains his charcoal black body coloring, along with gray fur.
- Mono- is Greek for one, chromi- is Greek for color, and -corn is presumably short for unicorn ("one-horn", via "rainicorn"). Monochromicorn means one color unicorn, as reference to his body's black coloration.
- He seems to have a slight physical appearance to Shadow Horse.
- Much like Cake, Lord Monochromicorn is not only a different gender than Lady Rainicorn, but also a different species.
- Lord Monochromicorn is a boss in These Lumps.