The Chao  are creatures that appear in the Sonic the Hedgehog series. Their role in the games are to be raised by the player in mini-games, similar to many virtual pets. Chao are somewhat complex: they respond to stimuli, have moods, require food and can be loving or fearful.

The Dark Chao are bad Chao children on the Dark side who are violent and like to play pranks. They like dark and mysterious places. Dark Chao can usually only speak one word which is their own species' name. However, they have a very distinct form of communication: their emotion-dot. The emotion-dot, which floats above a Dark Chao's head will change shape depending on what it thinks or feels: It becomes a heart when the Dark Chao is happy, a question mark when the Dark Chao is confused, an exclamation point when the Dark Chao is alarmed, and a swirl when the Dark Chao is unhappy. 

https://www.youtube.com/watch?v=Tjp3ndB5GtA Do your best in just trying to intimate this but making it slightly more mischievous and