So my friend's Discord had an art contest where we had to design our own Heartless based on any Disney movie. Below is the detailed explanation:

So I based my heartless design in the Zootopia universe. I don't know if you've seen the movie or not, but the core plot of the movie is the predators of the city are becoming feral and attacking prey animals, and it's because of a plant that grows natively in the rabbit parts of the city called Night Howlers, which Judy's dad uses to keep bugs away from his crops. When an animal ingests it, the plant's toxins affect the animal psychologically and decreases activity in most parts of the brain except for the cerebellum, which becomes hyperstimulated, causing the animal to go berserk.

So this heartless is a predatory animal "affected" by the plant. The blue-ish color and stem thingies sprouting from its head are reminiscent of the Night Howler plant. The tip of its tail also blooms to reveal the plant. The yellow coat and mask are references to the scene where Nick and Judy find a Breaking Bad-esqe lab where animals were extracting the toxins from the plant and using them in special guns that infect predatory animals.

And, of course, Heartless eyes lol